Direct Current Power Plant

ABSTRACT

A DC power plant generating DC power from a variety of engines including a Stirling cycle engine. The DC power plant includes a relatively small start-up power source that is discontinued after the engine is running. A method for producing DC power for a load including starting up an engine using power supplied by a relatively small power supply supplemented by a capacitor bank, providing output from the engine to a generator, producing alternating current (AC) power by the generator, converting the AC power to direct current (DC) power, disabling output of the DC power during a first set of pre-selected conditions, limiting a rate of change of current of the DC power during a second set of pre-selected conditions, reducing conducted and radiated emissions of the DC power, disconnecting the DC power from the load under a third set of pre-selected conditions, and providing the DC power to the load.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/182,182, filed Jun. 19, 2015, and entitledDirect Current Power Plant, (Attorney Docket No. Q25), and U.S.Provisional Patent Application Ser. No. 62/188,240, filed Jul. 2, 2015and entitled Direct Current Power Plant (Attorney Docket No. Q38), eachof which is hereby incorporated by reference in its entirety. Thepresent application is related to U.S. patent application Ser. No.13/827,140, filed Mar. 14, 2013 and entitled Modular Power ConversionSystem (Attorney Docket No. K37), which is a Continuation-In-Part ofU.S. patent application Ser. No. 13/447,897 ('897), filed Apr. 16, 2012and entitled Modular Power Conversion System, now U.S. Publication No.US-2013-0099565-A1, published Apr. 25, 2013 (Attorney Docket No. J36),which claims priority to U.S. Provisional Patent Application Ser. No.61/476,153, filed Apr. 15, 2011 and entitled Modular Power ConversionSystem, Method and Apparatus (Attorney Docket No. I37), each of which ishereby incorporated by reference in its entirety.

BACKGROUND

The present teachings relate to generating power and power electronics,and more specifically to generating direct current (DC) power.

Electricity generation is traditionally accomplished by large generatingplants such as nuclear reactors, hydro-electric dams, coal, and gasfired boilers. The electric power that is generated is stepped up to ahigher voltage, the voltage at which it connects to the transmissionnetwork. The transmission network can move, i.e. “wheel”, the power longdistances until it arrives at a local utility distribution networkwhere, at a substation, the power can be stepped down in voltage from atransmission level voltage to a distribution level voltage. As the powerexits the substation, it enters the distribution network. Finally, uponarrival at the service location such as a residential home or commercialuser, the power is stepped down again from the distribution voltage tothe required service voltage(s).

The traditional grid has limitations including, but not limited to,operational overhead, potential for widespread outages, agingtechnology, and security vulnerabilities. The traditional grid, alongwith its regional distinctions, is currently subject to the introductionof more efficient and smarter, although often smaller power generationtechnologies. Regional and local grids are now subject to low leveldispersed power generation from regional large and small windapplications, small hydro-electric facilities, and even commercial andresidential photovoltaic installations, for example. As such regionaland local power producers come on-line, the characteristics of powergeneration can, in some new grids, be entirely opposite of those listedherein. The characteristics of regional and local power producers couldbe attractive for some locales, and can be implemented in the form ofwhat is termed a “smart grid” using a combination of new design optionssuch as net metering, electric cars as a temporary energy source, and/ordistributed generation.

Of recent interest is the local generation and distribution of power, inparticular, DC power. Many appliances require a conversion from thegrid's AC power supply to DC power, which adds to the inefficienciesalready inherent in centralized power transmission from large remotepower generators. EMERGE® Alliance is an open industry associationdeveloping standards for DC power distribution. Current standardsinclude DC power distribution in interiors, and desktop/telecomstandards. Alternatively, DC power can be provided to the grid throughcommercially available inverters, and can be used in local powerdistribution facilities.

An example of a system that produces DC power is described in U.S. Pat.No. 7,701,705, a free-piston Stirling engine driving an alternator tosupply power through a bus to a user load. In this system, the engine isoperated at its maximum piston stroke, and the battery is charged ifneeded, when the bus voltage is in the range between a design nominalbus voltage (V₁) and a design minimum battery charging bus voltage (V₂).This system could benefit from an efficient means for starting theengine. Exemplary start-up circuits, such as for example, the onedescribed in U.S. Pat. No. 8,957,710, include a detection circuit and atransition circuit for preventing the problem of incapability intransition as well as achieving the purpose of low power consumption.These types of systems lack a means to discontinue current flow to thestart-up circuits when the engine is operating.

What is needed is a system to provide DC power from an engine to power aload and to power the control of the system, the system having arelatively small start-up power supply.

BRIEF SUMMARY

The needs set forth herein as well as further and other needs andadvantages are addressed by the present configurations, which illustratesolutions and advantages described below.

In accordance with one aspect of the present teachings, a modular powersystem is disclosed. The system can include a backplane, a housing and adata connection port, and one or more modules that can plug into thebackplane, wherein the backplane can include at least one direct current(DC) bus with positive and negative leads, a data connection for eachmodule, connections for electrical power inputs to the module,connections for electrical outputs from the module.

In some configurations, the modular power system can include amicroprocessor, one or more half-bridge circuits, power conditioningelements such as inductors, capacitors, voltage and current sensors, andelectrical connections. In some configurations, the modular power systemcan control rotating power generators including, but not limited to,diesel gensets, Stirling gensets, and wind power, to produce DC power,and may connect to an electrical shunt. In some configurations, one ormore of the microprocessors can control the power flow that can tocontrol the DC bus voltage to a given set-point.

In some configurations, a method for producing DC power for a load caninclude, but is not limited to including, starting an engine using powersupplied by a relatively small power supply supplemented by a capacitorbank, providing output from the Stirling engine to a generator,producing alternating current (AC) power by the generator, convertingthe AC power to direct current (DC) power, and providing the DC power tothe load. The method can optionally include disabling output of the DCpower during a first set of pre-selected conditions, limiting a rate ofchange of current of the DC power during a second set of pre-selectedconditions, reducing conducted and radiated emissions of the DC power,disconnecting the DC power from the load under a third set ofpre-selected conditions, and controlling velocity of the Stirling engineby a motor drive power board. The method can further optionally includeinhibiting current flow from the motor drive power board to thecapacitor bank, powering, by a second power supply at the starting up ofthe Stirling engine, system control electronics, shunting excess of theDC power in the form of heat produced by the Stirling engine into ashunt load, heating water with the heat, and controlling velocity of theStirling engine by a motor drive power board and the generator. Thefirst set of pre-selected conditions can include, but is not limited toincluding, overcurrent and ground fault conditions. The second set ofpre-selected conditions can include, but is not limited to including,abnormal conditions. The third set of pre-selected conditions caninclude, but is not limited to including, an abnormal overcurrentcondition. Disconnecting the DC power can include, but is not limited toincluding, shunt tripping a DC output breaker during an arc faultcondition. The method can optionally include providing the DC power toan igniter power board, a pump/fan/blower drive, an engine control I/OPCB, a system control PCB, and a power control PCB.

In some configurations, a system for producing DC power for a load caninclude, but is not limited to including, a Stirling engine initiallypowered by a relatively small power supply supplemented by a capacitorbank, a permanent magnet synchronous motor generator (PMSMG) operablycoupled to the Stirling engine, the PMSMG producing AC current from theoutput of the powered Stirling engine, a motor drive power boardoperably coupled to the PMSMG, the motor drive power board convertingthe AC current to DC power, and an ARC fault detector operably coupledto the EMI filter and a DC output breaker, the ARC fault detector shunttripping the DC output breaker during a series ARC fault condition, theDC output breaker providing the DC power to the load when a third set ofpre-selected conditions is false. The system can optionally include a DCoutput board operably coupled to the motor drive power board, the DCoutput board disabling output of the DC power from the motor drive powerboard during a first set of pre-selected conditions. The system canfurther optionally include a di/dT limiter operably coupled to the DCoutput board, the di/dT limiter limiting a rate of change of currentflow of the DC power from the DC output board during a second set ofpre-selected conditions. The system can still further optionally includean EMI filter operably coupled to the di/dT limiter, the EMI filterreducing conducted and radiated emissions of the DC power from the di/dTlimiter. The system can also optionally include a diode inhibitingcurrent flow from the motor drive power board to the capacitor bank. ThePMSMG can optionally control the velocity of the Stirling engine. Thefirst set of pre-selected conditions can include, but is not limited toincluding, overcurrent and ground fault conditions. The second set ofpre-selected conditions can include, but is not limited to including,abnormal conditions. The third set of pre-selected conditions caninclude, but is not limited to including, an abnormal overcurrentcondition. The PMSMG can include, but is not limited to including, a3-phase generator. The motor drive power board can include, but is notlimited to including, a 12 kVA, 3-phase, 4 quadrant AC/DC converter. TheEMI filter can include, but is not limited to including, a 50A filter.The DC output breaker can include, but is not limited to including, a50A breaker. The DC power can include, but is not limited to including,390 VDC. The capacitor bank can include, but is not limited toincluding, 24.6 mF. The system can optionally include a system controlpower source, and a start-up system control power source. The relativelysmall power supply can include, but is not limited to including, a 380VDC @ 4A power supply. The system can optionally include a motorcontroller for a permanent magnetic synchronous motor that can include,but is not limited to including, an analog/digital converter thatconverts analog sensor signals from the permanent magnetic synchronousmotor to digital signals for use by a digital signal processorcomprising half bridges across a DC bus and aninductor-capacitor-inductor filter that produce three phase AC power ata predetermined voltage and frequency, at least one voltage sensor andat least one current sensor for three-phase demodulation of the threephase signals and converting the three-phase signals to a two-phaseorthogonal reference frame, and a position/velocity estimator forreceiving speed sensor signals from the motor and compiling a positionand velocity estimation of the motor.

In some configurations, the system can include a brake module. In someconfigurations, the motor drive for the permanent magnetic synchronousmotor can include an analog/digital converter that can convert analogsensor signals from the permanent magnetic synchronous motor to digitalsignals for use by a digital signal processor, at least one voltagesensor and at least one current sensor for three-phase demodulation ofthe three phase signals, and a position/velocity estimator for receivingspeed sensor signals from the motor and compiling a position andvelocity estimation of the motor.

In some configurations, a method for starting a Stirling engine caninclude, but is not limited to including, powering a first AC powersupply, powering a second AC power supply, starting the Stirling engineby the first AC power supply and a capacitor bank, and starting systemcontrol electronics by the second AC power supply. The system controlelectronics can control a power control board, and the power controlboard can control the Stirling engine.

In some configurations, a method for operating a DC power plant caninclude, but is not limited to including, driving a generator usingoutput from a running Stirling engine, producing a 3-phase AC current bythe generator, converting the AC current to the DC power. And providingthe DC power to internal loads internal to the DC power plant and toexternal loads external to the DC power plant. The method can optionallyinclude measuring voltage and frequency of a grid supply, reporting thevoltage and frequency via CANbus to a system controller, starting theengine if the grid supply is within a pre-selected range of tolerance,and recording the voltage and frequency in a continuously running logfile. The method can further optionally include receiving an angle froma sawtooth waveform generator, representing the angle by a 16-bit value,applying an average increment to the angle, as the angle sweeps from0-360°, every 100 secs, the average increment having a 32-bit centerfrequency input and a 16-bit delta frequency input driven by a PIcontroller, the center frequency input representing a fractional valueof the angle, the delta frequency oscillating about zero, producing asine/cosine pair for the angle, creating an inverter output waveformbased on the sine/cosine pair, computing a phase error signal based onthe sine of the angle and the voltage of the grid supply, the voltage ofthe grid supply being equal to the cosine of the voltage of the gridsupply, multiplying the sine by the voltage of the grid supply toproduce a signal that contains both AC and DC components, the ACcomponent having an amplitude variation based on the amplitudes of thegrid supply and the inverter output waveform and having a frequencyequal to 2× the frequency of the grid supply when the loop is locked,the DC component having an amplitude variation based on the phase errorbetween the grid supply and the inverter output waveform, low passfiltering the phase error, and eliminating a part of the AC componentnot relevant to control by supplying the filtered phase error to the PIcontroller.

In some configurations, the method of the present teachings forproducing DC power for a load can include, but is not limited toincluding, starting up an engine using power supplied by a relativelysmall power supply supplemented by a capacitor bank, providing outputfrom the engine to a generator, producing alternating current (AC) powerby the generator, converting the AC power to direct current (DC) power,disabling output of the DC power during a first set of pre-selectedconditions, limiting a rate of change of current of the DC power duringa second set of pre-selected conditions, reducing conducted and radiatedemissions of the DC power, disconnecting the DC power from the loadunder a third set of pre-selected conditions, and providing the DC powerto the load.

These aspects of the present teachings are not meant to be exclusive andother features, aspects, and advantages of the present teachings will bereadily apparent to those of ordinary skill in the art when read inconjunction with the appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

These and other features and advantages of the present invention will bebetter understood by reading the following detailed description, takentogether with the drawings wherein:

FIG. 1 is a pictorial representation of a configuration of the powersystem of the present teachings;

FIG. 2 is a pictorial representation of a configuration of a modularpower conversion system;

FIG. 3 is a schematic block diagram of a configuration of a powerconversion system;

FIGS. 4A-4F are schematic diagrams of a configuration of an engine-basedDC power plant;

FIGS. 4G-4J are schematic block diagrams of an exemplary configurationof the DC power plant of the present teachings;

FIGS. 5A-5C are schematic diagrams that together represent an individualphase lock loop building block of some configurations;

FIGS. 5D-5I are schematic diagrams that together represent dual phaselock loops of some configurations;

FIG. 6 is a schematic block diagram of the velocity controller statemachine of the present teachings;

FIG. 7 is a schematic block diagram of one configuration of the feedbackloop for adjustments to rotor speed of the present teachings;

FIG. 8 is a schematic block diagram of another configuration of thefeedback loop for adjustments to rotor speed of the present teachings;

FIG. 9 is a diagrammatic representation of state and transition valuesof a configuration of the velocity controller state machine of thepresent teachings;

FIG. 10 is a flowchart of state and transition values of a configurationof the velocity controller state machine of the present teachings;

FIG. 11 is a flowchart of the method of one configuration of the presentteachings.

FIG. 12 is a graphical representation of the Stirling engine torqueaccording to one configuration of the present teachings;

FIG. 13 is a schematic diagram of an alternative engine startingalgorithm according to one configuration of the present teachings;

FIGS. 14A-O are tables including CAN bus message header definitions ofthe present teachings;

FIGS. 15A-15C are tables including exemplary data in CAN messages;

FIG. 16 is a schematic block diagram of the communications links andtransmissions of an embedded power electronics system according to oneconfiguration of the present teachings;

FIG. 17 is a flow chart of a configuration of the use of a Session ID toconfirm an interruption in the communications and transmissions of anembedded power electronics system of the present teachings;

FIG. 18 is a schedule table and data palette of the communications linksand transmissions of an embedded power electronics system according toone configuration of the present teachings; and

FIGS. 19A-19B are representations of a method to annotate softwarevariables in an embedded system according to one configuration;

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

A configuration of the DC power plant is discussed in detail below inrelation to a thermal engine, in this case a Stirling engine. However,various other Stirling engines may be used. The system may beconsolidated in a cabinet and interconnected for example via an isolatedController Area Network (CAN) 2.0b or other electrical interface(s) thatcan facilitate communication and data processing between controllers andcomputers. In more complex systems further modules may be added tohandle additional electrical resources. The system may include an LCDfront display panel having multiple graphical user interfaces for systemstatus monitoring and control inputs. Alternatively, a personal computermay be accommodated by USB, Ethernet, internet, wireless or other knowncommunications format, to enable monitoring and control of the DC powerplant.

Referring now primarily to FIG. 1, generator 11 and exemplary heat sink17A can be interconnected with modular power production system 212.Exemplary heat sink 17A can also include a power sink that can, forexample, connect an electrical resistor that can dissipate excesselectrical power from DC bus 250 (FIG. 4E) by converting it to heat. Insome configurations, the power from DC bus 250 (FIG. 4E) may bepurposely directed to brake module 19A (FIG. 4H) to create heat as theprimary purpose of the system. A generator module can include a powersource that can convert the polyphase electrical power from engine 11into DC power primarily for residential load 28A. In someconfigurations, Stirling engine 11A (FIG. 3), as described in U.S.patent application Ser. No. 12/829,320 filed Jul. 1, 2010, now U.S.Publication No. US-2011-0011078-A1 published Jan. 20, 2011 and entitledStirling Cycle Machine (Attorney Docket No. 178), which is herebyincorporated herein by reference in its entirety, may generate power insome configurations.

Referring now primarily to FIG. 2, modular power production system 212can consolidate power control 39 (FIG. 3), including hardware andsoftware, in an interchangeable modular or “block” format. It is thegoal of this format to be able to generate and provide DC power from,for example, but not limited to, Stirling engine 11A (FIG. 3), wind,thermal, and photovoltaic to load 28 (FIG. 3). Power production 214 caninclude, but is not limited to including, in some configurations,electricity production and communication between “electric resources”and for example, but not limited to, electricity production from lowlevel producer(s) such as, for example, but not limited to, Stirlingengine 11A (FIG. 3), wind turbine, or photovoltaic array. Electricitycan be provided to load 28 (FIG. 3) such as, for example, but notlimited to, a commercial or residential building, directly. An electricresource can be an electrical entity that can act as load 28 (FIG. 3),generator 11 (FIG. 1), or storage. In modular power production system212, each module or “block” is interchangeable to facilitate powerproduction 214 and power consumption 220. The term digital signalprocessor (DSP) may be used herein to describe any micro-processor withsufficient input/output and speed to read voltages, currents, controlmultiple sets of half-bridge circuits. In some configurations, the DSPmicroprocessor can run at 150 MHz. System controller 53 (FIG. 3) formodular power production system 212 may include a data input/outputdevice such as a keyboard and display or a touch-sensitive display orcommunication port to allow users to control the operation of modularpower production system 212. Modular power production system 212 mayalso include a wireless or hard wired telecommunication ability to allowremote control and access to the system data. An alternativeconfiguration may place all the computing power in a master controller.Thus the operation of each module could be fully under the control ofone or more DSPs in the master controller.

Referring now primarily to FIG. 3, Stirling engine 11A, which can becontrolled by system controller 53A through engine controller 49, canproduce a mechanical output that can drive, for example, but not limitedto, permanent magnet synchronous motor (PMSM) 13. Other motors arepossible such as, for example, but not limited to, an induction motorand a synchronous reluctance motor. PMSM 13 can be controlled orconditioned to effectively run as an AC motor/generator providingconsistent three-phase power to load 28 despite the variable torquegenerated by Stirling engine 11A. Charging a battery system (not shown)can overcome variable torque. The battery system can receive incomingpower, no matter any torque or power fluctuations from the input and/ormotor, and can store the power for application to load 28. In someconfigurations, PMSM 13 can be controlled with power controller 39including, for example, but not limited to, motor power board 15 andbrake chopper 19A (FIG. 4H). Power controller 39 may also receive dataand information from system controller 53A.

Continuing to refer primarily to FIG. 3, in some configurations, enginepower output can be matched to the DC power demand from externallyconnected and variable loads 28. Efficiency can be improved if engine 11(FIG. 4G), for example Stirling engine 11A, does not produce power thatis in excess of what is demanded. If excess power is produced, the powercan be dissipated through, for example, but not limited to, shunt load17 (FIG. 4H) and brake chopper 19A (FIG. 4H). The engine power outputcan be kept slightly higher than load 28 so that there is a buffer ofavailable power for instantaneous supply that can cover a pre-selectedincrease in demand. Power control board 39 can continuously communicateto motor power board 15 indicating the present state of the powerexcess. Power excess can be calculated by observing the amount of powerbeing dissipated in the combination of, for example, but not limited to,shunt load 17 (FIG. 4H) and brake chopper 19A (FIG. 4H). Power controlboard 39 can control igniters 29 (FIG. 4G). In some configurations,igniters 29 (FIG. 4G) can require a power supply of approximately 120VDC at approximately 8 amps. Power control board 39 can include a voltagecontroller and a current controller that can use conventionalproportional-integral (PI) controllers with voltage and current feedbackcircuits. Power control board 39 can also include logic that can includepre-selected voltage and current regulation values. The voltageregulation value can act as reference input to the voltage controllerwhich can provide a current regulation reference to the currentcontroller, while the current regulation value can act as a limit to thecurrent reference value produced by the voltage controller. A third PIcontroller can reduce the power being supplied to the igniters 29 (FIG.4G) by monitoring the system DC voltage level to ensure that igniters 29(FIG. 4G) do not rob the system of power when it may be needed for otherpurposes. Note that system 100 (FIG. 4G) can produce DC power forigniters 29 (FIG. 4G) as well as motor power board 15, DC output board19, and pump, fan, and blower drive 34 (FIG. 4I). The third PIcontroller can reduce the current regulation limit value that acts uponthe current controller. By restricting the amount of current that canflow through igniters 29 (FIG. 4G), the power consumed by igniters 29(FIG. 4G) can be reduced in proportion. In some configurations, thecurrent limit control can be reduced to zero.

Referring now primarily to FIGS. 4A-4F, in some configurations, majorcomponents of second DC power plant configuration can include, but arenot limited to including, start-up power components 103A (FIG. 4F),power controller 105A (FIG. 4E), Stirling engine 11A (FIG. 4D), sensors109A (FIGS. 4A/4C), and system controller 107A (FIG. 4A). In operation,power from start-up power components 103A (FIG. 4F) can be sent to motor13 (FIG. 4F) which can supply torque to start Stirling engine 11A (FIG.4D). Start-up power components 103A (FIG. 4F) can also send power tosystem controller 107A (FIG. 4A) and power controller 105A (FIG. 4E).Burner 301 (FIG. 4B), fueled by, for example, but not limited to,propane or natural gas, can ignite and heat a working gas that canmaintain motion in Stirling engine 11A (FIG. 4D). After Stirling engine11A (FIG. 4D) comes up to speed, it can send energy back to motor 13(FIG. 4B) which can act as a generator sending power to systemcontroller 107A (FIG. 4A), power controller 105A (FIG. 4E), and to DCload 28 (FIG. 4E). Start-up power components 103A (FIG. 4F) can be takenout of the circuit by diode 38 (FIG. 4F) so that power frommotor/generator 13 (FIG. 4B) can flow to the other parts of system 300without flowing back to start-up power components 103A (FIG. 4F). Whenmotor/generator 13 (FIG. 4B) is generating power, power from start-uppower components 103A (FIG. 4F) for system controller 107A (FIG. 4A) andpower controller 105A (FIG. 4E) can become unnecessary.

Continuing to refer primarily to FIGS. 4A-4F, in some configurations,Stirling engine 11A (FIG. 4D) can contain a working fluid and burner 301(FIG. 4B) for heating the working fluid of Stirling engine 11A (FIG.4D), an airlock space separating the crankcase and the working space formaintaining a pressure differential between the crankcase housing andthe working space housing and airlock pressure regulator 303 (FIG. 4D)connected between the crankcase and one of the airlock space and workingspace. System controller 107A (FIG. 4A) can process a number of failsafetriggers based on sensor data from sensors 109A (FIGS. 4A/4C) andcontroller evaluation algorithms that can evaluate system 300 anddetermine if system 300 should be turned to shut-down or stop mode.Levels of heat, power, and oxygen, for example, can be monitored andshut-down or engine stoppage can be performed, or other modifications tosystem 300 and Stirling engine 11A (FIG. 4D), if a temperature readingis too high, or if exhaust oxygen level is too high, or if engine speedexceeds a desired value, or if the differential pressure within the airlock is too low, for example. These are exemplary triggers for startingshut-down or stop procedures, other triggers could be used as well or incombination with these examples.

Continuing to refer primarily to FIGS. 4A-4F, system 300 can includeblower 305 (FIG. 4E) that can provide air or other gas for facilitatingignition and combustion in burner 301 (FIG. 4B). System 300 can alsoinclude a preheater (details not shown) that can, for example, but notlimited to, define an incoming air passage and an exhaust passageseparated by an exhaust manifold wall that can, for example, but notlimited to, heat incoming air from the hot exhaust expelled from theheating element, a fuel injector (details not shown) that can, forexample, but not limited to, supply fuel to mix with the incoming air,igniter 29 (FIG. 4B) that can, for example, but not limited to, ignitethe fuel/air mixture, a prechamber (details not shown) that can, forexample, but not limited to, define an inlet for receiving the fuel/airmixture and promote ignition of the mixture, a combustion chamber(details not shown) that can, for example, but not limited to, bedisposed linearly below the prechamber that can, for example, but notlimited to, maintain supporting a flame developed and ignited in theprechamber, and an electronic control unit (details not shown) that can,for example, but not limited to, control ignition and combustionoperations of burner 301 (FIG. 4B), and wherein the combustion chambercan be connected to the exhaust passage into which the exhaustedcombustion gases are pushed to heat the incoming air followingcombustion and heating of the engine or machine. During normal engineoperation, blower 305 (FIG. 4E) can be operated at least partially by acontrol loop which can measure the excess oxygen in the exhaust todetermine blower speed. Failsafe triggers can include when engine speedexceeds a predetermined range, oxygen levels in exhaust exceed apredetermined range, generator temperature exceeds a predeterminedrange, burner temperature exceeds a predetermined range, coolertemperature exceeds a predetermined range, flame/ignition failure,and/or repeatable failure of flame ignition, for example. The describedcontrol method is not limited to the disclosed triggers and othertriggers, factors, and variables may also be analyzed by systemcontroller 107A (FIG. 4A) under the start-up and operation modes.

Continuing to still further refer primarily to FIGS. 4A-4F, systemcontroller 107A (FIG. 4A) may be separate from but connected to and incommunication with power controller 105A (FIG. 4E) and a hardware schemethat facilitates conversion of mechanical to electrical energyessentially downstream from Stirling engine 11A (FIG. 4D). Someconfigurations of the power electronics may be those described in '897.System controller 107A (FIG. 4A) can provide Stirling engine 11A (FIG.4D) operational control including, but not limited to, regulation of anairlock such as, for example, but not limited to, the airlock describedherein as well as for example burner(s) 301 (FIG. 4B). Blower 305 (FIG.4E) can provide the air flow for combustion in burner(s) 301 (FIG. 4B),as well as cooling of a burner enclosure. System controller 107A (FIG.4A) can control the air flow via a speed command passed to variablefrequency drive (VFD) 35 (FIG. 4I). A blower speed signal may provide afeedback signal to system controller 107A (FIG. 4A) which can permit,for example, but not limited to, evaluation and control of the blowerdrive by the system controller 107A (FIG. 4A).

Still further referring primarily to FIGS. 4A-4G, in someconfigurations, for each burner 301 (FIG. 4B), flame detection module 47(FIG. 4B) can be provided for safety, temperature control, and theignition process among other things. In some configurations, igniter(s)29 (FIG. 4B) for each burner 301 (FIG. 4B) can be directly influenced byflame sensors 307 (FIG. 4B) through system controller 107A (FIG. 4A),and igniter(s) 29 (FIG. 4B) can be controlled via igniter signal lines309 (FIG. 4B) based on the flame sensor data and other data from theengine such as oxygen sensors, for example. In various configurations,coolant flow and temperature can be inputs to system controller 107A(FIG. 4A) to control coolant flow pump 311 (FIG. 4E) and ensure thatappropriate coolant temperature is maintained in Stirling engine 11A(FIG. 4D). In some configurations, airlock delta pressure regulator(AdPR) 343 (FIG. 4D) can be directly connected and controlled via systemcontroller 107A (FIG. 4A). In some configurations, system controller107A (FIG. 4A) may also communicate with power controller 105A (FIG. 4E)over CAN bus 313 (FIG. 4A) but could also, in some configurations, relyon wireless communications or other communications protocols such asUSB. System controller 107A (FIG. 4A) may, in some configurations,command the speed of motor/generator 13 (FIG. 4F). Configurations ofpower electronics as they relate to control and monitoring ofmotor/generator 13 (FIG. 4F) may be those described in '897. In someconfigurations, system controller 107A (FIG. 4A) and power controller105A (FIG. 4E) may exchange data and commands including, but not limitedto, motor drive velocity command, generator velocity, bus voltage, buscurrent, motor drive IGBT bridge temperature, shunt control, shuntactive, battery voltage, battery temperature, inverter power, inverterenable, inverter PWM, inverter voltage inverter current, invertertemperature, converter power, converter enable, converter PWM, convertervoltage, converter current, and converter temperature. In someconfigurations, the term converter refers to one or more DC/DC convertercircuits. Certain direct inputs into system controller 107A (FIG. 4A)may also be necessary and can include but are not limited to including,oil temperature from the crankcase, battery temperature, motortemperature, and shunt temperature.

Referring now primarily to FIGS. 4G-4J, components of system 300 (FIGS.4A-4F) important to the improvements of some configurations are shown insystem 100 for producing DC power for load 28 (FIG. 4H). System 100 caninclude, but is not limited to including, engine 11 (FIG. 4G) initiallypowered by relatively small power supply 41 (FIG. 4J) supplemented bycapacitor bank 37 (FIG. 4G). System 100 can further include PMSM 13(FIG. 4G) operably coupled to engine 11 (FIG. 4G). PMSM 13 (FIG. 4G) canconvert electrical energy to mechanical energy (torque) to providerequired startup for engine 11 (FIG. 4G). PMSM 13 (FIG. 4G) can act as agenerator powered by engine 11 (FIG. 4G) after engine 11 (FIG. 4CG is upto speed, and can provide AC current to motor power board 15 (FIG. 4G).Motor power board 15 (FIG. 4G) can convert the AC current to DC power.System 100 can also include DC output board 19 (FIG. 4H) operablycoupled to motor power board 15 (FIG. 4G). DC output board 19 (FIG. 4H)can disable output of the DC power from motor power board 15 (FIG. 4G)during a first set of pre-selected conditions. System 100 can includedi/dt limiter 21 (FIG. 4H) operably coupled to DC output board 19 (FIG.4H). di/dt limiter 21 (FIG. 4H) can limit a rate of change of currentflow from DC output board 19 (FIG. 4H) during a second set ofpre-selected conditions. di/dt limiter 21 (FIG. 4H) can be acost-effective way to control current flow from DC output board 19 (FIG.4H). In some configurations, di/dt 21 (FIG. 4H) can include, forexample, a toroidal core constructed and available from, for example,but not limited to, micrometals.com as powdered iron alloy #2. Corematerial #2 is characterized by the property that it does not saturate.System 100 can further include EMI filter 23 (FIG. 4H) operably coupledto di/dt limiter 21 (FIG. 4H). EMI filter 23 (FIG. 4H) can reduceconducted and radiated emissions of the DC power from di/dt limiter 21(FIG. 4H). System 100 can still further include ARC fault detector 25(FIG. 4H) operably coupled to EMI filter 23 (FIG. 4H) and DC outputbreaker 27 (FIG. 4H). ARC fault detector 25 (FIG. 4H) can shunt trip DCoutput breaker 27 (FIG. 4H) during a series ARC fault condition. DCoutput breaker 27 (FIG. 4H) can provide the DC power to load 28 (FIG.4H) when a third set of pre-selected conditions is false. The first setof pre-selected conditions can optionally include overcurrent and groundfault conditions, the second set of pre-selected conditions canoptionally include abnormal conditions, and the third set ofpre-selected conditions can optionally include an abnormal overcurrentcondition.

Continuing to refer primarily to FIGS. 4G-4J, resolver 59 (FIG. 4G) is aposition measurement device used for commutation of PMSM 13 (FIG. 4G).The fuel source for engine 11 (FIG. 4G) can be, for example, but notlimited to, propane gas or natural gas. PMSM 13 (FIG. 4G) can be used asa motor initially to start engine 11 (FIG. 4G). Once engine 11 (FIG. 4G)is turning and producing power, PMSM 13 (FIG. 4G) can be used as agenerator to control the velocity of engine 11 (FIG. 4G) and extractpower from engine 11 (FIG. 4G). PMSM 13 (FIG. 4G) can be brought up toan approximate alternator electrical speed before it locks(synchronizes) to a selected rotational rate. Once up to speed, PMSM 13(FIG. 4G) can maintain synchronism with the AC power source, can developtorque, and can maintain a constant speed. When PMSM 13 (FIG. 4C) is3-phase 4-pole, for example, it can generate an electrically rotatingfield in the stator. The three phases of stator excitation can addvectorially to produce a single resultant magnetic field which canrotate at 1800 rpm with 60 Hz power or 1500 rpm with 50 Hz power. System100 can include motor power board 15 (FIG. 4G), including a 3-phase,4-quadrant AC/DC converter used for velocity control of PMSM 13 (FIG.4G). System 100 can further include DC output board 19 (FIG. 4H)including brake chopper 19A (FIG. 4H), output enable and protection 19B(FIG. 4H), and shunt trip control 19C (FIG. 4H). DC output board 19(FIG. 4H) can be operably connected to power control board 39 (FIG. 4H)and resolver 59 (FIG. 4G). Brake chopper 19A (FIG. 4H) can limit DC busvoltage by, for example, but not limited to, switching the excess energyto shunt load 17 (FIG. 4H). Output enable and protection 19B (FIG. 4H)can disable output power from the DC output terminals during overcurrentor ground fault conditions. Shunt trip control 19C (FIG. 4H) can controlthe fault conditions under which shunt trip 61 (FIG. 4H) is driven. Thefault conditions can include, but are not limited to including, arcfault, ground fault, and unexpected loss of control power.

Continuing to refer primarily to FIGS. 4G-4J, system 100 can furtherinclude di/dt limiter 21 (FIG. 4H), EMI filter 23 (FIG. 4H), arc faultdetector 25 (FIG. 4H), and DC output breaker 27 (FIG. 4H). di/dt limiter21 (FIG. 4H), operably electrically coupled with DC output board 19(FIG. 4H) and EMI filter 23 (FIG. 4H), can provide series inductance tolimit current rate of change under abnormal conditions. Commerciallyavailable EMI filter 23 (FIG. 4H) (for example, but not limited to,50A), operably electrically coupled with di/dt limiter 21 (FIG. 4H) andarc fault detector 25 (FIG. 4H), can reduce conducted and radiatedemissions. Commercially available arc fault detector 25 (FIG. 4H),operably electrically coupled with EMI filter 23 (FIG. 4H) and DC outputbreaker 27 (FIG. 4H), can shunt trip DC output breaker 27 (FIG. 4H)during a series arc fault condition. Commercially available DC outputbreaker 27 (FIG. 4H) (for example, but not limited to, 50A), operablyelectrically coupled with arc fault detector 25 (FIG. 4H) and theexternal load, can disconnect the DC power plant + and − terminals fromexternal load 28 (FIG. 4H) in the event of an abnormal overcurrentcondition. Arc fault detector 25 (FIG. 4H) can be operably connected toshunt trip 61 (FIG. 4H) and shunt trip control 19C (FIG. 4H). DC outputbreaker 27 (FIG. 4H) can be operably connected to shunt trip 61 (FIG.4H).

Continuing to refer primarily to FIGS. 4G-4J, system 100 can alsoinclude igniters 29 (FIG. 4G), hot surface ignition sources, thatestablish flame in burner 301 (FIG. 4B). System 100 can also includeigniter power board 31 (FIG. 4G) (for example, but not limited to, 400VDC to 120 VDC, 600 W), a DC/DC buck converter used to drive hot surfaceigniters 29 (FIG. 4G), with which igniter power board 31 (FIG. 4G) canbe operably electrically connected. Igniters 29 (FIG. 4G) and igniterpower board 31 (FIG. 4G) can be powered by startup DC bus power 41 (FIG.4J) during startup, and by PMSM 13 (FIG. 4G) while system 100 is in runmode. Igniter power board 31 (FIG. 4G) can be operably connected topower control board 39 (FIG. 4H). System 100 can also include pump, fan,and blower drive 34 (FIG. 4I) including induction motor 33 (FIG. 4I) andvariable frequency drive 35 (FIG. 4I) (VFD) used to drive inductionmotor 33 (FIG. 4I) to cool engine 11 (FIG. 4G). VFD 35 (FIG. 4I) can beoperably connected to engine control I/O PCB 49 (FIG. 4I). Pump, fan,and blower drive 34 (FIG. 4I) can include combustion air blower 305(FIG. 4E) providing combustion air to burner 301 (FIG. 4B). A combustionair pressure switch to prevent fuel flow if combustion air blower 305(FIG. 4E) flow is low can also be included. Coolant pump 311 (FIG. 4E)can also be included that provides coolant flow to engine 11 (FIG. 4G)used to maintain proper engine temperatures. Fuel control modulatingvalve 315 (FIG. 4A) can modulate a gas valve that controls fuel flowinto burner 301 (FIG. 4B) to regulate heat transfer surface temperatureof engine 11 (FIG. 4G). Fuel regulator 317 (FIG. 4A) can regulate fuelpressure into burner 301 (FIG. 4B). Radiator fan 319 (FIG. 4E) canprovide system cooling to maintain temperature differential that drivesengine 11 (FIG. 4G). Pressure vessel overpressure relief device 321(FIG. 4D) can limit the pressure in a pressure vessel under abnormalconditions. The pressure vessel can contain helium working gas forengine 11 (FIG. 4G). Power burner 301 (FIG. 4B) can provide heat to theheat transfer surface of engine 11 (FIG. 4G) to create heat differentialthat can drive, if engine 11 (FIG. 4G) is Stirling engine 11A (FIG. 4D),the Stirling cycle. Heater head high-limit thermocouple 325 (FIG. 4C) isa hardware safety overtemp that can provide equipment protection. Ahelium fill system can be used to maintain proper helium pressure in theStirling engine pressure vessel. The fill system can include heliumbottle 323 (FIG. 4D), pressure transducer, gas pressure regulator 329(FIG. 4D), and solenoid valve 327 (FIG. 4D). Main gas valve 331 (FIG.4B) can be a dual solenoid valve that isolates system 100 from a maingas supply. Fuel valve interlock contacts 333 (FIG. 4A) or optionalcontacts can be included that can be wired to a remote on/off switch, aCO detector, and/or a heat alarm. An airlock can separate a wetlubricated sump from a dry workspace. The airlock can include adifferential pressure transducer and an electric pump motor for closedloop control of airlock pressure.

Continuing to refer primarily to FIGS. 4G-4J, system 100 can optionallyinclude diode 38 (FIG. 4G) inhibiting current flow from motor powerboard 15 (FIG. 4G) to capacitor bank 37 (FIG. 4G) as discussed herein.PMSM 13 (FIG. 4G), along with motor power board 15 (FIG. 4G) and enginecontrol board 49 (FIG. 4I), can control engine 11 (FIG. 4G). PMSM 13(FIG. 4G) can optionally be a 3-phase generator. Motor power board 15(FIG. 4G) can provide 12 kVA, and be a 3-phase, 4 quadrant AC/DCconverter. In some configurations, EMI filter 23 (FIG. 4H) can include a50A filter, DC output breaker 27 (FIG. 4H) can include a 50A breaker, DCpower can be delivered at 390 VDC, relatively small power supply 41(FIG. 4J) can supply 380 VDC @ 4A, and the capacity of capacitor bank 37(FIG. 4G) can be a function of the starting torque. In someconfigurations, more or less power can be supplied, where each otherpower component can be scaled according to the overall systemrequirements. System 100 can include system control power source 45(FIG. 4I) and start-up system control power source 43 (FIG. 4J). Powercontrol board 39 (FIG. 4H) and system control board 53 (FIG. 4J) canoptionally include commercially available hardware and software toimplement controller area network (CAN) bus 313 (FIG. 4J). Exemplarymessages exchanged over CAN bus 313 (FIG. 4J) are described herein.System 100 can further include engine control input/output (I/O) board49 (FIG. 4I) operably connected to start-up control power 43 (FIG. 4J),external on/off control 58 (FIG. 4I), and system control power 45 (FIG.4I). Engine control board 49 (FIG. 4I) can be powered at start-up bystart-up control power 43 (FIG. 4H), and then during operation by engine11 (FIG. 4G) through system control power 45 (FIG. 4I).

Continuing to refer primarily to FIGS. 4G-4J, system 100 can include atleast one start-up DC bus power 41 (FIG. 4J), an AC mains-derived DCpower supply used during engine starts. Start-up DC bus power 41 (FIG.4J) can supply power to DC bus 250 (FIG. 4E) and ultimately engine 11(FIG. 4G), and can derive its power from AC power source 63 (FIG. 4J).In some configurations, start-up DC bus power 41 (FIG. 4J) can supply,for example, but not limited to, 380 VDC @ 4A. When that is not enoughpower to start engine 11 (FIG. 4G), at least one motor start capacitorbank 37 (FIG. 4G) can supply some of its stored energy to start engine11 (FIG. 4G). Motor start capacitor bank 37 (FIG. 4G) can be sized at,for example, but not limited to, 24.6 milli-Farads. The pairing ofstart-up DC bus power 41 (FIG. 4H) with motor start capacity bank 37(FIG. 4G) can allow start-up DC bus power supply 41 (FIG. 4H) to berelatively smaller than a power supply that would alone supply peakpower required for start-up of engine 11 (FIG. 4G). DC bus power 41(FIG. 4H) can optionally be enabled which can be powered, at start-up,by start-up control power 43 (FIG. 4H), an AC mains-derived DC powersupply used during engine starts that can supply power (for example, butnot limited to, 23 VDC @ 5A) to engine control I/O board 49 (FIG. 4I),system control board 53 (FIG. 4J), and power control board 39 (FIG. 4H).After engine start-up and current flow begins, diode 38 (FIG. 4G) canprevent current from flowing into motor start capacitor bank 37 (FIG.4G) and start-up DC bus power 41 (FIG. 4J). Further, when engine 11(FIG. 4G) is operational, it can supply current to power subsystem 105A(FIG. 4I), which can replace start-up control power 43 (FIG. 4J) as thepower supply for control subsystem 107A (FIG. 4A) by providing a highervoltage, for example, but not limited to 24 VDC @ 5A, relative to thepower of start-up control 43 (FIG. 4J) which can be, but is not limitedto being, 23 VDC @ 5A.

Referring still primarily to FIGS. 4G-4J, system control power 45 (FIG.4I) can be the power supply on DC bus 250 (FIG. 4E) that can supplypower to system and power controllers at 24 VDC @ 12A. Someconfigurations of power control board 39 (FIG. 4H) are described in partin United States Patent Application #s 2013-0099565, 2014-0091622, WO2014/152706, and 2015-0084563, all entitled Modular Power ConversionSystem. In some configurations, Modular Power Conversion System, uponwhich power control board 39 (FIG. 4H) can be based, can convert anyform of electrical power to any other form of electrical power andoptimize the available sources and loads based on real time pricing anddemand variables without grid feedback. Power control board 39 (FIG. 4H)can be an embedded control and acquisition system that can include adigital signal processor, I/O and peripherals. Power control board 39(FIG. 4H) can send control signals to motor power board 15 (FIG. 4G), DCoutput board 19 (FIG. 4H), and igniter power board 31 (FIG. 4G). Thecontrol signals can include, but are not limited to including,conventional low voltage differential signaling (LVDS) gate controlsignals. Other control signals can include LVDS Bridge Fault and StatusSignals and inter-integrated circuit communication signals. Powercontrol board 39 (FIG. 4H) can monitor 240 VAC 63 through monitor line3130 (FIGS. 4H/4J). System 100 phase locks to 240 VAC input 63 (FIG. 4J)to measure voltage and frequency and report these via CANbus 313 (FIG.4J) to system control board 53 (FIG. 4J). System control board 53 (FIG.4J) can, for example, but not limited to, decide whether to allow anengine start sequence depending on whether 240 VAC 63 (FIG. 4J) appearsto be within acceptable tolerances. System control board 53 (FIG. 4J)can also record the reported voltage and frequency in a continuouslyrunning log file. The recorded frequency measurement may indicate whenan externally attached grid-forming inverter is using a frequency shiftmethod of signaling a change in power demand to other attached grid tiedinverters.

Referring again primarily to FIGS. 4G-4J, system 100 can further includeengine control I/O board 49 (FIG. 4I), including VFD control 49A (FIG.4I), hardware safety interlock 49B (FIG. 4I), I/O and sensor interface49C (FIG. 4I), and system control interface 49D (FIG. 4I). System 100can also include system control board 53 (FIG. 4J) that can enable, forexample, but not limited to, embedded control and acquisition. Enginecontrol I/O board 49 (FIG. 4I) can be powered by startup DC bus power 41(FIG. 4J) until engine 11 (FIG. 4G) is running. Engine control I/O board49 (FIG. 4I) can be operably connected to system control board 53 (FIG.4J), and emergency power off (EPO) switch 57 (FIG. 4I). System controlboard 53 (FIG. 4J) can be operably connected to external computercontroller 55 (FIG. 4J) (and ultimately network 20 (FIG. 4J)). Externalon/off control 58 (FIG. 4I) can include, but is not limited toincluding, a contact closure that can be used to signal system 100 tostart. Engine control I/O board 49 (FIG. 4I) can include, but is notlimited to including, commercially available components such as, forexample, National Instruments (NI) cRIO 9023, NI 9112 FPGA 8 slotchassis, NI 9213 Thermocouple module, NI 9426 Digital Input Module, NI9477 Digital Output Module, ONI 9205 Analog Input Module, NI 9264 AnalogOutput Module, NI 9505 DC Servo Drive Module, NI 9375 Digital IO Module,and NI 9853 CAN Communications Module.

Continuing to refer primarily to FIGS. 4G-4J, system 100 can furtherinclude, but is not limited to including, system I/O and sensors 51(FIG. 4I) and flame detect module 47 (FIG. 4I). Flame detect module 47(FIG. 4I) can, for example, but not limited to, monitor the presence offlame in burner 301 (FIG. 4B); the monitoring can avoid accumulation ofunburnt fuel in a burner system. Parameters that can be sensed by systemI/O and sensors 51 (FIG. 4I) can include, but are not limited toincluding, (1) motor stator inner thermistor 344 (FIG. 4C) that canmonitor stator temperature of PMSM 13 (FIG. 4G) for equipmentprotection, (2) airlock pressure sensor 347 (FIG. 4D) that can maintainproper helium pressure in engine 11 (FIG. 4G), (3) coolant flow sensor337 (FIG. 4F) that can monitor coolant flow in system 100 where themonitoring can protect engine 11 (FIG. 4G), (4) coolant pressure reliefvalve 341 (FIG. 4F) that can limit the pressure in the cooling systemunder abnormal conditions, (5) cooler thermistor 343 (FIG. 4C) that canmonitor coolant temperature in engine 11 (FIG. 4G) for equipmentprotection and control, (6) a crankcase pressure sensor (not shown) thatcan monitor bulk working gas pressure in a pressure vessel of engine 11(FIG. 4G), (7) exhaust gas oxygen sensor 349 (FIG. 4D) that can monitorthe oxygen level in burner exhaust gas and for closed loop control of afuel/air ratio, (8) flame temperature thermocouple sensor 351 (FIG. 4C)that can monitor the temperature of a power burner flame, (9) swirlerthermocouple 353 (FIG. 4C) that can monitor air preheat temperature in aburner recuperator, (10) heater head thermocouple 355 (FIG. 4C) that canmonitor the temperature of a heat transfer surface of engine 11 (FIG.4G), (11) oil pressure sensor 357 (FIG. 4D) that can monitor oilpressure in engine 11 (FIG. 4G) for equipment protection, and (12) oiltemperature thermistor 361 (FIG. 4D) that can monitor oil temperature inengine 11 (FIG. 4G), where the monitoring can protect the equipment.

Referring now primarily to FIGS. 5A-5C, phase lock loop (PLL) 500 (FIG.5A) can integrate frequency-based grid connection safety features intosystem 100 (FIGS. 4C-4F). PLL 500 (FIG. 5A) can include sawtoothwaveform generator 509 (FIG. 5B) that can provide angle θ 507 (FIG. 5B)to polynomial calculation 561A which can produce sine and cosine pair(quadrature) 509 (FIG. 5B) for angle θ 507 (FIG. 5B). Angle θ 507 (FIG.5B) can be constantly swept from 0° through 360° (via sawtooth 505 (FIG.5B)) at rate (i.e. frequency) which can be varied, for example, but notlimited to, under software control to achieve an operating frequency of60 Hz+/−approximately 6 Hz. To achieve phase lock with the grid, a phaseerror signal can be derived by multiplying sine 563 (FIG. 5A) of thephase lock loop reference by the grid voltage Vab which is assumed to bea sinusoidal signal also operating at approximately 60 Hz. At this step,the voltage Vab is taken to be cosine 565 (FIG. 5A) of the grid voltage.By multiplying sine 563 (FIG. 5A) of the reference by cosine 565 (FIG.5A) of the grid, a signal 567 (FIG. 5A) is produced which contains bothan AC and a DC component. The AC component will vary in amplitudeaccording to the amplitudes of the reference and the grid, and will havea frequency of 2× the grid frequency once the loop is locked. The DCcomponent will vary in amplitude according to the phase error betweenthe reference and the grid. Since the reference and the grid form aquadrature pair, the phase error will be zero when they are 90° apart.With a known phase error 557 (FIG. 5B), PI controller 503 (FIG. 5B) canbe applied to create a closed loop control which can drive phase error557 (FIG. 5B) to zero by modulating frequency. In some configurations,system 100 (FIGS. 4C-4F) can operate within the constraints offixed-point integer math and a fixed frequency (10 kHz) carrier rate.The 10 kHz carrier rate means that angle θ 507 (FIG. 5B) is updated onceevery 100 sec. Angle θ 507 (FIG. 5B) is represented by an unsigned16-bit value where zero=0° and 2¹⁶-1=359.995°.

Continuing to refer to FIGS. 5A-5C, to achieve a frequency of 60 Hz,angle θ 507 (FIG. 5B) must sweep from 0° through 360° in 16.6 ( 1/60)msec with a constant increment applied once every 100 μsec (the carrierperiod). This increment can be calculated as follows: (65536/10000Hz)×60 Hz=393.216 where 65536=360° as represented by the angle θ, 10000Hz=carrier frequency, and 60 Hz=desired angle θ→frequency. Fixed pointinteger math cannot produce a non-integral increment on an individualcarrier. The nearest two integral values (in this case 393 and 394) areinterleaved so that the average increment equals the exact requiredincrement over some number of carriers, referred to herein as fractionalclock division. Fractional clock divider 551 (FIG. 5C) can follow PIcontroller 503 (FIG. 5B), and can utilize a combination of 32-bit centerfrequency input 553 (FIG. 5C) (e.g. 60 Hz) and a 16-bit delta frequencyinput 555 (FIG. 5C) which can be driven by PI controller 503 (FIG. 5B).32-bit center frequency value 553 (FIG. 5C) can allow directrepresentation of the fractional increment value where the deltafrequency input allows PI controller 503 (FIG. 5B) to operate in itsnatural bipolar mode centered on zero. Even operating at a fixedfrequency (holding delta frequency at a constant) the output of clockdivider 551 (FIG. 5C) will not be a constant, but, in the case of a 60Hz system, the output of clock divider 551 (FIG. 5C) will be togglingbetween 393 and 394 in a predictable pattern. Thus, the instantaneousvalue of output from clock divider 551 (FIG. 5C) may not be able to beused as a direct indication of operating frequency because the value isconstantly changing. Frequency measurement accuracy and/or PLL stabilitycan be affected by the AC component (sinusoidal) in phase error signal557 (FIG. 5B). Feeding phase error 557 (FIG. 5B) into PI controller 503(FIG. 5B) can cause the error to propagate directly through PIcontroller 503 (FIG. 5B) which could cause the instantaneous value ofthe frequency to be incorrect. Using low pass filter 501A (FIG. 5A) tofilter phase error 557A (FIG. 5A) before supplying it to PI controller503 (FIG. 5B) could eliminate most of the AC component which is notrelevant to the control.

Referring now primarily to FIGS. 5D-5I, in an exemplary use of the logicfrom FIGS. 5A-5C, dual PLLs can be used in system 100 (FIGS. 4C-4F) tomonitor grid voltage and frequency. Specifically, first digital phaselocked loop (DPLL) 500A (FIG. 5E) can track grid voltage and frequencywhen the voltage and frequency are within tolerance. Second DPLL 500B(FIG. 5H) can continuously measure and report grid frequency 561 (FIG.5H) and phase error 559 (FIG. 5H), and can remain locked over as wide arange as possible. Grid voltage measurement can be referenced to secondDPLL 500B (FIG. 5H). Conditions that can be required for PLL lock arethat (1) absolute error must be less than a threshold, and (2) inputvoltage must be within a threshold. Low pass filter 501B (FIG. 5E) canbe used to filter the output of first DPLL 500A (FIG. 5E) to improve PLLperformance.

Referring now primarily to FIG. 6, velocity control for PMSM 13 caninclude power electronic circuit 722 for 3-phase PMSM 13. Other controlloop structures may also be used to control PMSM motor/generator 13 orother motors as well. Analog/digital (A/D) converter 752 can convertanalog sensor signals from PMSM motor 13 to digital signals for use bydigital signal processor (DSP) 754. Digital Hall sensors (not shown) canbe used to eliminate A/D converter 752. Voltage sensors 262 and currentsensors 260 can be provided for 3-phase demodulation of the three phasesignals ABC and, applying Clarke/Park transforms, given sin/cos of theelectrical angle, the 3-phase signal can be converted to a 2-phaseorthogonal (xy) reference frame, and then from the stationary referenceframe to the rotor (dq) reference frame for vector current loop 764.Each of the Clarke/Park orthogonal reference frame transform 760 androtor reference frame transform 762 have different scaling andnormalization factors and circuitry can be provided to preventsaturation of the output duty cycle and allow significant amplitude tobe added to the net output duty cycle. Position/velocity estimator 766can receive signals from motor velocity sensor 753 sensing the velocityof PMSM motor 13, as well as orthogonal reference frame transform 760,and can compile a position and velocity estimation of PMSM motor 13.Vector current loop 764, orthogonal reference frame transform 760, rotorreference frame transform 762, PWM registers 756, 3-phase bridge 758,and position velocity estimator 766 can execute in a motor velocitycontrol loop 768 which can receive commands from system control board 53via power control board 39 to directly control PMSM motor/generator 13.

Continuing to refer primarily to FIG. 6, Stirling engine 11A (FIG. 3)does not produce constant output torque, so as it operates, the torqueoscillates up and down. To control the motor torque of PMSMmotor/generator 13 and hence the velocity, vector current feedback loop764 can be used so that the variable torque from Stirling engine 11A(FIG. 3) and the resultant DC power do not detrimentally effect PMSMmotor/generator 13. Vector control of PMSM motor/generator 13 can beused with a velocity control state machine using essentially threedifferent control states: start-up, starting and running states.Position/velocity estimator 766 can estimate position/velocity throughinformation provided by position sensors, for example resolver 59 (FIG.3), or three Hall sensors (not shown) at, for example, 60°. DC bussensor 753A can provide DC bus status information to A/D converter 752.

Referring now primarily to FIG. 7, using Hall sensors in their statelessform it is possible to decode the sector from the Hall sensor andcompute position increment and unwrap, which can provide a raw Hallangle and an indication of which positional motor segment the rotor isin. In order to obtain the necessary motor speed estimate for motorpower board 15 (FIG. 3), the position can be differentiated, or afeedback loop can be used. Method 9150 can include estimating 9100 rotorspeed and integrating 9101 estimated speed to get an estimated rotorposition. Method 9150 can further include receiving 9102 a Hall sensordigital signal and obtaining 9103 from the digital signal a raw estimateof angle of the rotor with each 60° step of the motor cycle, andunwrapping 9104 the raw estimate bit by extending the lowest significantbits of the sensor information over time to obtain a bit extended inputposition. Method 9150 can include transforming 9105 a sawtooth errorfrom the Hall sensor by putting the input position through a deadbandblock. The deadband range can compensate for the +30° and −30° limit ofknown natural error of a Hall sensor. The deadband range is 70-80% ofthis limit of natural error and therefore everything outside the errorwhich exists within the deadband range may be essentially disregardedand/or moved towards a zero value. Error may also be limited by the useof techniques and methods for dynamically setting limits on thecommanded current. Method 9150 can further include comparing 9106 theestimated rotor position to the measured rotor position from the Hallsensor(s) to produce an error term. Method 9150 can include computing9107 a position error based on the error term, and changing 9111 theinitial speed estimate based on the position error. Method 9150 canoptionally include if 9108 the error is greater than an error threshold,clipping 9110 the difference between the estimated position and themeasured position. Method 9150 can further optionally include if 9108the error is less than or equal to the error threshold, if 9109 theerror is less than or equal to the error threshold, using the estimatedrotor speed. Current limits can be used in electronic circuitry in orderto prevent excessive current that may result in catastrophic failure ofelectronic components, in this case motor/generator 13 (FIG. 3). In someconfigurations, the generation of commands for current which can preventthe current from exceeding a dynamically predetermined limit can beused. The limit may be determined for example as a function of powerdissipation in a component as estimated from a measured current leveland as a function of a measured temperature proximate to the component.Other methods and techniques for limiting current are possible as well.Some of these are described in U.S. Pat. No. 6,992,452, entitled DynamicCurrent Limiting, issued on Jan. 31, 2006, and hereby incorporated byreference.

Continuing to refer primarily to FIG. 7, if an input sensor hasinaccuracies, for example, if a Hall sensor is inaccurate to 30°, or aresolver is inaccurate to 5°, the input sensor can override if the errorbetween input sensor and estimate is too high. For example, if the Hallsensor measurement is 5° different from the raw input estimate, then theestimated value can be used. If the error is within 70°, the differencebetween the Hall sensor and the estimate can be clipped to a desiredrange, for instance an error threshold of 35-45°. The error value can belimited to a band around the angle. Other threshold errors could also beused as well.

Referring now primarily to FIG. 8, in some configurations, the feedbackloop of FIG. 7 may use a resolver instead of Hall sensors. Method 10150can include estimating 10100 the rotor speed, and integrating 10101 theestimated speed to obtain an estimated rotor position. Method 10150 canfurther include receiving 10202 resolver digital signal 56 (FIG. 4E) andcalculating 10203 a measured position of the rotor based on resolverdigital signal 56 (FIG. 4E). Method 10150 can also include comparing10106 the estimated rotor position to the measured rotor position fromthe resolver, and calculating 10107 a position error based on thecomparison. Method 10150 can include changing 10111 the initial speedestimate based on the position error. In some configurations, obtainingan accurate measured rotor angle position can be aided by the use oflimiters, i.e. current limiting methods and techniques, as well asdeadbands based on resolver performance. Method 10150 can optionallyinclude applying 10105 a deadband range to the measured rotor positionwhich can transform the sawtooth error from the resolver, narrowing themeasured input position value that can then be compared to the estimatedposition. The deadband range can compensate for the +5° and −5° degreelimit of known natural error of a resolver. The deadband range can be70-80% of this limit of natural error and therefore everything outsidethe error which exists within the deadband range may be essentiallydisregarded and/or moved towards a zero value. Error may also be limitedby the use of techniques and methods for dynamically setting limits onthe commanded current. Method 10150 can further optionally include if10108 the error is greater than an error threshold, clipping 10110 thedifference between the estimated position and the measured position.Method 10150 can further optionally include if 10109 the error is lessthan or equal to the error threshold, using 10109A the estimated rotorspeed.

Referring now primarily to FIG. 9, a difficulty in controlling thevelocity based on input from Stirling engine 11A (FIG. 3) is that thetorque τ_(st) of Stirling engine 11A (FIG. 3) has high spatialharmonics: τ_(st)==τ₀+τ₁ f(⊖_(m)) where τ₀ and τ₁ are functions of theslowly changing variables of head temperature and pressure, and f(⊖_(m))is a periodic function of angular position with respect to amplitude. Atstart-up of Stirling engine 11A (FIG. 3) the start-up torque τ_(st) isnegative and typically varies significantly as Stirling engine 11A (FIG.3) turns through a complete revolution. One of the pistons of Stirlingengine 11A (FIG. 3) compresses gas during part of a revolution leadingto more negative torque. In a later part of the revolution, the pistonallows the gas to expand producing a less negative torque or even apositive torque. This change in torque over small angles i.e.τ_(st)≈−k⊖_(m) can lead to highly variable torque output. This effectcan occur during the cycle of Stirling engine 11A (FIG. 3), but can bemore significant during startup as the slow engine speed does notproduce a flywheel effect to coast through the more negative torqueperiods. Once Stirling engine 11A (FIG. 3) is rotating, the inertia ofStirling engine 11A (FIG. 3) can be enough to maintain a more constant,but still somewhat variable torque. Following start-up, because theaverage torque of a cycle is positive and the time over which the torqueharmonics act is inversely proportional to speed, the peak speedfluctuations are inversely proportional to average speed. But atstart-up, a velocity controller (motor velocity control loop 768 (FIG.6)) for PMSM 13 (FIG. 3) may exert a motor torque τ_(m) which could begreater than the peak negative “springy” torque generated in start-up inorder to get Stirling engine 11A (FIG. 3) rotating. At start-up, it canbe preferable that the motor torque τ_(m) increases at a steady rateuntil it exceeds a lower threshold r_(max) _(_) _(neg) and Stirlingengine 11A (FIG. 3) accelerates. The rate of torque increase cannotoccur too slowly otherwise start-up will take too long to start and themotor power board 15 (FIG. 3) can risk overheating. If the torqueincrease is too fast, more motor torque than necessary may be producedand motor power board 15 (FIG. 3) may not be able to tell how muchtorque is actually needed.

Further referring primarily to FIG. 9, motor power board 15 (FIG. 3)could counteract or dampen the “springiness” of Stirling engine 11A(FIG. 3) at low speeds, and not use excess torque in acceleratingStirling engine 11A (FIG. 3). The costs of excess torque can be excessheating and excess power draw. Also, start-up and starting torque mayexceed average running torque by a factor of two or three in someengines, so it could be start-up and starting torque that can dictatethe peak power handling capability of motor power board 15 (FIG. 3). Aproportional-integral (PI) controller of speed can be used in someconfigurations. When Stirling engine 11A (FIG. 3) is rotating atsufficient speed, motor torque Tm can counteract the average torque ofStirling engine 11A (FIG. 3) and can maintain roughly constant speed.Motor power board 15 (FIG. 3) can yield generated power from PMSM 13(FIG. 3) as a side effect of speed control. After Stirling engine 11A(FIG. 3) is running, the same PI controller gains used for start-up andstarting states can be modified for use at running speeds. At runningspeeds, the gains can be low so that motor power board 15 (FIG. 3) doesnot fight the oscillating torque fluctuations of Stirling engine 11A(FIG. 3). The gains can maintain a slowly changing generating torque tocounteract the average torque from Stirling engine 11A (FIG. 3), whileallowing moderate speed fluctuation.

Referring still primarily to FIG. 9, in some configurations, thedifferences between start-up and running torque can be addressed byutilizing a velocity controller state machine with three (3) states,although other numbers of states could also be determined. Power controlboard 39 (FIG. 10) can initiate in start-up state 870 and, afterpredetermined first speed threshold 872 is exceeded, power control board39 (FIG. 10) can enter starting state 874. When second predeterminedspeed threshold 876 is exceeded, power control board 39 (FIG. 10) canshift to running state 878.

Referring now primarily to FIG. 10, each of the three states can have adifferent integral gain Ki and different proportional gain Kp. The statetransition condition for each speed threshold is |ω_(m)|<thresh_lo or|ω_(m)|>thresh_hi where ω_(m) is the measured or estimated motorvelocity. A maximum speed command max_cmd parameter can limit the inputto the velocity control loop 768 (FIG. 6) to be within the range of+/−max_cmd. Kp and Ki can be tuned according to the desired behavior ofeach state. As an example of some parameter sets for entering start-upstate 870, entering starting state 874, and entering running state 878,method 979 can show these three states and transition values as follows:

Start-Up:

Kp, Ki tuned for optimal torque ramp rate

Thresh_lo=0

Thresh_hi=600 rpm

Max_cmd=650 rpm (transition to starting state when speed >600 rpm justslightly greater than the transition threshold.)

Starting:

Kp, Ki tuned for fast speed control without overshoot

Thresh_lo=0

Thresh_hi=900 rpm

Max_cmd=950 rpm (transition to starting state when speed >900 rpm justslightly greater than the transition threshold.)

Running:

Kp, Ki tuned for low bandwidth speed control;

Thresh_lo=600

Thresh_hi=spd_max (max detectable speed)

Max_cmd=spd_max (no limit)

Continuing to refer primarily to FIG. 10, method 979 for controlling thespeed of motor 13 (FIG. 3) can include, but is not limited to including,entering 981 startup state 870, tuning 982 the integral gain and theproportional gain for a steady state increase. If 983 the torque isgreater than the maximum negative torque, and if 984 the motor speed isgreater than 600 rpm, entering 985 starting state 874. If 983 the torqueis less than or equal to the maximum negative torque, returning to step982. If 984 the motor speed is less than or equal to 600 rpm, returningto step 981. Method 979 can further include tuning 986 gain for speedcontrol, no overshoot. If 991 the motor speed is greater than 900 rpm,entering 987 running state 878. If 991 the motor speed is less than orequal to 900 rpm, returning to step 986. Method 979 can also includetuning 988 gain for low bandwidth control. If 989 the motor speed isgreater than 600 rpm, and if 990 the motor speed is greater than amaximum detectable speed, returning to running state 987. If 989 themotor speed is less than or equal to 600 rpm, returning to step 988. If990 the motor speed is less than or equal to the maximum detectablespeed, entering 981 start-up state 870.

Referring now primarily to FIG. 11, with respect to three operatingstates, method 150 for producing DC power for a load can include, but isnot limited to including, starting 151 an engine using power supplied bya relatively small power supply supplemented by a capacitor bank,providing 153 output from the engine to a generator, producing 155alternating current (AC) power by the generator, converting 157 the ACpower to direct current (DC) power, disabling 159 output of the DC powerduring a first set of pre-selected conditions, limiting 161 a rate ofchange of current of the DC power during a second set of pre-selectedconditions, reducing 163 conducted and radiated emissions of the DCpower, disconnecting 165 the DC power from the load under a third set ofpre-selected conditions, and providing 167 the DC power to the load.

Continuing to refer primarily to FIG. 11, method 150 can optionallyinclude controlling velocity of the motor by a motor drive power boardas commanded by a system control board via a power control board, andinhibiting current flow from the motor drive power board to thecapacitor bank. Method 150 can further optionally include powering, by asecond power supply at the starting up of the engine, system controlelectronics. Method 150 can still further optionally include shuntingexcess of the DC power in the form of heat produced by the Stirlingengine into a shunt load and heating water with the heat. Method 150 canalso optionally include controlling velocity of the motor by a motordrive power board and the generator. The first set of pre-selectedconditions can optionally include, but is not limited to, overcurrentand ground fault conditions. The second set of pre-selected conditionscan optionally include, but is not limited to including, abnormalconditions. The third set of pre-selected conditions can optionallyinclude, but is not limited to including, an abnormal overcurrentcondition. Disconnecting the DC power can optionally include shunttripping a DC output breaker during an arc fault condition. Method 150can optionally include providing the DC power to an igniter power board,a pump/fan/blower drive, an engine control I/O PCB, a system controlPCB, and a power control PCB.

Referring now primarily to FIG. 12, one alternative to the aboveparameters is to override motor speed in all states besides the runningstate, instead of limiting it. Controlling the motor speed with afeedback PI loop, for example, on the motor speed depends on varyinginstantaneous motor speed over each revolution during starting as torque3001 varies. Thus, in some configurations, an adaptive estimate of theamplitude and phase of speed fluctuation using low pass filtering (LPF)3101 (FIG. 13) can remove noise and thus subtract out as much of thefluctuation as possible, so that the PI loop does not need to respond tothis fluctuation.

Referring now primarily to FIG. 13, the amplitude and phase may changevery slowly, so quadrature demodulation may allow amplitude componentresolution. Speed signal 3103 can be filtered to remove frequencies muchhigher than the speed ripple. Speed signal 3103 can be passed through asynchronous demodulated algorithm to produce Kc 3105 and Ks 3107. Thetime varying values of Kc 3105 and Ks 3107 are the sinusoidal componentsof speed ripple that are at 900 from each other. Note that the low passfilters 3101 of the demodulator algorithm and the computation 3109 ofω_(m) are different. The ripple-free or average speed isω_(m)′=ω_(m)−Kc*cos(ω_(m))−Ks*sin(ω_(m)) and the control speed is basedon this estimate of ω_(m)′. In a further configuration of motor controlarchitecture, a vector control motor which may use variable frequencydrives to control the torque, and thus the speed of 3-phase electricmotor/generators by controlling the current fed to the machine, can beused. Different motor types are possible such as induction motors,permanent magnet synchronous motors (PMSM), and synchronous reluctancemotors (Synch Rel) for instance with PMSM motors used by way of examplefor some configurations. In PMSM motors, the permanent magnets on therotor are pulled in one direction or another by the relative position ofthe stator and rotor fields. Because the rotor field is fixed inorientation with the rotor, torque production and control requiresknowledge of rotor position.

Referring again primarily to FIG. 6, there are a number of ways to writethe torque equation for PMSM motor 13, for example:

$V_{dq} = {{K_{e}\omega_{m}} = {{RI}_{dq} + {L_{dq}\frac{I_{dq}}{t}} + {J\; \omega_{e}L_{dq}I_{dq}}}}$

where V is the terminal voltage, I is the motor current, K_(e) is theback-emf constant, ω_(m) is the mechanical rotational frequency of therotor, ω_(e)=ω_(m)P/2 is electrical rotational frequency of the rotor, Pis the number of poles, and L and R are the inductance and resistance.The equation is written in the rotor (dq−) reference frame with

${J = \begin{bmatrix}0 & {- 1} \\1 & 0\end{bmatrix}},{V_{dq} = \begin{bmatrix}V_{d} \\V_{q}\end{bmatrix}},{I_{dq} = \begin{bmatrix}I_{d} \\I_{q}\end{bmatrix}},{L_{dq} = \begin{bmatrix}L_{d} & 0 \\0 & L_{q}\end{bmatrix}},{K_{e} = \begin{bmatrix}0 \\\frac{2\lambda \; m}{P}\end{bmatrix}}$

where λm=rotor magnet flux, which may then be used to write out thestate equation in scalar form as

$V_{d} = {{RI}_{d} - {\omega_{e}L_{q}I_{q}} + {L_{d}\frac{I_{d}}{t}}}$$V_{q} = {{K_{e}\omega_{m}} + {RI}_{q} + {\omega_{e}L_{d}I_{d}} + {L_{q}\frac{I_{q}}{t}}}$

The cross terms (with ω_(e)) result from reference frame rotation(similar to Coriolis “force”); in the stator (xy−) reference frame, theyare not present but the

$L_{d}\frac{I_{d}}{t}$

and K_(e)ω_(m) terms are present. The cross terms can couple the twoequations at nonzero speed. The torque equation is

$\tau_{m} = {{\frac{3}{2}\left( {{\frac{P}{2}\left( {L_{q} - L_{d}} \right)I_{q}I_{d}} + {K_{e}I_{q}}} \right)} = {\frac{3}{2}\frac{P}{2}\left( {{\left( {L_{q} - L_{d}} \right)I_{q}I_{d}} + {\lambda_{m}I_{q}}} \right)}}$

which includes a reluctance torque term due to rotor saliency(L_(q)≠L_(d)) and an alignment torque term. In some configurations PMSMmotor 13 with a torque control loop structure could utilize a sine-driveor a six-step drive. The six-step drive could be a good match fordigital Hall sensors. Utilizing a sine-drive, the choice of torque loopmay be decoupled from the choice of position/speed sensor.

Referring now primarily to FIG. 14A, power controller 39 (FIG. 3) cancommunicate with motor power board 15 (FIG. 3), DC output board 19 (FIG.3), and igniter board 31 (FIG. 3) to control motor 13 (FIG. 3) as wellas Stirling engine 11A (FIG. 3). CAN bus 313 (FIG. 4J) can be used to,for example, but not limited to, enable communications among the varioussubsystems in power controller 39 (FIG. 3), system controller 53A (FIG.3), and various control actuators and/or receive feedback from varioussensors and ensure that the appropriate messages are timely delivered tothe appropriate subsystem to be evaluated and acted on by powercontroller 39 (FIG. 3). Each message from an electronic control unit ofpower controller 39 (FIG. 3) can be transmitted onto a data bus in whichmessage conflicts can be resolved using standard protocols. Conformingto Part B of the CAN specification 2.0, 1991, a CAN message can include,but is not limited to including, 29 bits of message identifier, fourbits of a data length field, and 0-8 bytes of data, among other fields.In some configurations, data can include, but is not limited toincluding, critical control flags, system faults/status, power stagefaults, overvoltage regulator faults/status, motor drive faults/status,buck/boost faults/status, inverter faults/status, and controller systeminformation. In the 29-bit extended mode message identifier, bits 0-28,message priority 11120 can be defined by the highest three bits—bits 28,27, 26—with zero being the highest priority. Priority of messages havingequal message priorities 11120 can be arbitrated by the contents ofother bits in the message identifier. In some configurations, thepriority zero (highest) can be used only for the most critical controland alarm functions. The highest bits can be used to define prioritybecause, similar to standard arbitration protocols, if two messages aretransmitted at the same time, as soon as a recessive (1 value bit) isseen for a lower priority message transmission, the message is stoppedand a higher priority message with a dominant (0 value bit) is sentunimpeded to CAN bus 313 (FIG. 3). For example, a message with the bits28, 27 and 26 set to zero can be the highest priority message that maybe sent. On the other hand if these same bits are all set to 1, this canbe the lowest priority that may be set for a message, but a recessivevalue at any bit location could stop transmission of the message ifanother message being transmitted has a dominant bit value at the samelocation. The impeded message can then be transmitted based on itspriority after the higher priority message. This can provide for a totalof eight different priority combinations or definitions where each bitis either 0 or 1 in binary notation, and with three bits the totalnumber of permutations is 2×2×2=8 combinations or definitions formessage priority 11120.

Continuing to refer primarily to FIG. 14A, the standard CAN protocoldoes not include system configuration information, for example,information about the destination of a message. Instead, all messagesare sent to all nodes. Nodes can decide whether to act upon data in themessage based on the contents of the message. Thus, any number of nodescan receive the message and act upon it simultaneously. Aftertransmission of the message priority 11120, the remainder of the bitscan be utilized as the message definitions body themselves and thesedefinitions can be divided into a series of groups, for example, but notlimited to: system group 11122 defined by three bits—25, 24,23—functional group 11124 defined by four bits—22, 21, 20 and 19—modulegroup 11126 defined by eight bits—18-11—device group 11127 defined bythree bits—11, 10, and 9—and message group 11128 defined by elevenbits—bits 10-0. Message priority 11120 and the groups do not have tocontain these specific bits or this exact number of bits described here,other allocations of bits may be provided as well. However, the CANprotocol interprets any zero bit value to trump any non-zero bit valuein terms of message priority 11120. Therefore, assigning bit values tomembers of groups can require evaluation of priority.

Continuing to still further refer primarily to FIG. 14A, system group11122 can include, for example, bit settings to identify powercontroller 39 (FIG. 3), for example, the setting of bits 23-25 to zero.Other configurations for power controller 39 (FIG. 3) may be assignedusing other bit value combinations. Functional group 11124 can identifysubgroups power production, power transmission, power consumption,energy storage, and utility by unique bit settings. In someconfigurations, power production messages can be assigned the highestpriority, which means setting of bits 19-22 to zero. Other subgroups maybe defined as well. Module group 11126 can identify various powerproduction, transmission, and consumption devices, for example enginessuch as diesel and gas generators, thermal engines such as Stirlingengines, wind turbines, photovoltaic systems, fuel cells, and for energystorage with battery storage systems and battery charging systems. Insome configurations, Stirling engine 11A (FIG. 3) can be assigned thehighest priority. In some configurations, there may be over 2000messages defined in message group 11128, and any given message may beidentified as important to any module in Module Group 11126. Thesespecific and unique identifiers not only readily allow orderlycommunication of messages across CAN bus 313 (FIG. 4J), but also tellthe controllers what the message is, and may contain associated measuredor sensed data which can permit the controller to determine appropriatecommands for controlling the various modules or system components.Device group 11127 can identify one of eight possible devices on the buswith otherwise identical attributes of system, function, and modelgroups.

Referring now primarily to FIG. 14B, in some configurations, a messageidentification field can include priority field 11120 occupying the mostsignificant of the 29-bit CAN message header to ensure that criticalsystem control messages do not get superseded by less importantmessages. Priorities identified in some configurations can include, butare not limited to including, National Instruments rugged andreconfigurable control and monitoring system (cRIO) to power electronicsmessages (highest priority, i.e. priority 0), power electronics to cRIO(priority 2), cRIO to power electronics variable frequency devicemessages (priority 3), and power electronics variable frequency deviceto cRIO messages (priority 4).

Referring now primarily to FIGS. 14C-G, in some configurations, systemgroup 11122 (FIG. 14C), functional group 11124 (FIG. 14D), module group11126 (FIGS. 14E and 14F), and device group 11127 (FIG. 14G) can includevarious bit configurations.

Referring now primarily to FIGS. 14H-14O, in some configurations,message characteristics for messages transferred among elements of thesystem can include critical messages (FIG. 14H) priority two messages(FIGS. 14I-14L), and priority three and four messages (FIGS. 14M-14O)For example, critical control flags 1122A for a 3-phase Stirlinggenerator have message ID 0x00005002, and message index two. Prioritytwo power electronics messages (FIGS. 14I-14L) can include 3-phaseStirling generator motor watts and brake watts messages 1122B, messageID 265, for example. Priority three and four power electronics messagesfor utility function, VFD module, and VFD combustion device (FIG. 14M)can include, for example, control flags 1122C, message index 2, andspeed 1122D, message index 256. Priority three and four powerelectronics messages for utility function, VFD module, and VFD waterpump (FIG. 14N) can include, for example, control flags, message indextwo and speed message index 256. Priority three and four powerelectronics messages for utility function, VFD module, and VFD waterradiator (FIG. 14O) can include, for example, control flags 1122E,message index 2 and speed 1122F message index 256.

Referring now primarily to FIG. 15A, critical control flags, message ID0x00005002, message index 2, can occupy two 16-bit words (four bytes)with bits set by system control board 53 (FIG. 8), for example. Systemcontrol board 53 (FIG. 3) can send a CAN message having specific bitsset to power control board 39 (FIG. 3) which in turn could use theinformation in the critical control flags to control motor power board15 (FIG. 3), igniter power board 31 (FIG. 3), and DC output board 19(FIG. 3). For example, if power control board 39 (FIG. 3) receives a CANmessage having data including message ID 0x00005002 followed by a 16-bitword with at least bit one 1122G set, power control board 39 (FIG. 3)could force itself to a faulted state. Likewise, if power control board39 (FIG. 3) receives a message according to CAN bus protocol having dataincluding message ID 0x00005002 followed by a 16-bit word with at leastbit two 1122H set, power control board could enable engine controller 49(FIG. 3). Message index 2 information is also shown in FIG. 14H.

Referring primarily to FIG. 15B, a first 16-bit word for systemfaults/status could be included in the data section of the CAN messagefor message ID 0x0800510C, message index 268. The word could, forexample, but not limited to, communicate status of various devices, forexample, but not limited to, shunt 17 (FIG. 4H). Message index 268information is also shown in FIG. 14J.

Referring primarily to FIG. 15C, VFD message details corresponding toutility VFD, VFD radiator (FIG. 14P) message information is shown. Ingeneral, each CAN message in the VFD message group can include fourwords of data, the exemplary contents of which can include, in someconfigurations, messages relating to speed, status, current, andvoltage, for example.

Referring now primarily to FIG. 16, measured or sensed data and otherarbitrary information from embedded power control board 39 can becollected in real-time to, for example, but not limited to, diagnoseerrors and/or debug issues. Digital signal processor (DSP) 19140 forexample can operably communicate with at least one device such ascomputer or PC 19142 via communications link 19144. Communications link19144 can be, but is not limited to being, a serial port or UART,Ethernet, Bluetooth wireless, or can accommodate other communicationprotocols. A relevant characteristic of communications link 19144 isthat there can be a stream of information flowing in each direction. Aprotocol can define several different types of packets of informationfor each direction of the protocol. DSP 19140 can transmit packets tothe PC 19142, some of which may include broadcast of arbitrary data. PC19142 can transmit packets to the DSP 19140, some of which are commandsto read or write data in DSP 19140, including data that can determinewhich data DSP 19140 should be broadcasting to PC 19142. This can allowfor changes at any time as to which data PC 19142 receives. In additionthere can be other packets that can allow DSP 19140 and PC 19142 todetermine whether communication link 19144 between the two ismaintained. If communication link 19144 is interrupted and resumed, astatus check of communication link 19144 between each of the devices andlinks with other devices within the system can be performed withdiagnostic checks that can determine if there are any changes inperformance of any of the devices. Further executable programs such asDiagUI 19200 may be installed on PC 19142 and may use communicationslink 19144 to transmit and receive data as discussed herein.

Referring again primarily to FIG. 16, the information available to bothDSP 19140 and PC 19142 can include how to communicate via a protocol, aswell as how to build metadata including the following data: (1) date andtime the DSP program was compiled, (2) a unique 128-bit ID generated perthe standard Universally Unique Identifier (UUID) mechanism, (3) aprogram identifier (a human-readable string to distinguish varying typesof DSP programs), (4) a version number that can corresponds to theversion of the source code stored in a source control repository such asSURROUND SCM®, CLEARCASE®, and/or SUBVERSION®. Metadata can be storedwithin executable file 19148 that can be generated at compile time. DSP19140 can be programmed using executable file 19148. PC 19142 can haveaccess to executable file 19148, as well as access to build metadata.Executable file 19148 can also have a DSP symbol table so that given thename of a variable on DSP 19140 that has a fixed memory location, PC19142 can determine what type of variable it is (e.g. 16-bit unsignedinteger, 32-bit pointer, structure, union, etc.), and where it islocated in the DSP's memory.

Continuing to refer primarily to FIG. 16, DSP 19140 may use, forexample, but not limited to, a 2.34375 Mbaud serial port with thestandard UART configuration of one start bit, eight data bits, and onestop bit per byte, or 234,375 bytes per second maximum throughput ineach direction. If a diagnostic kernel routine on the DSP executes at a10 kHz rate, then the diagnostic kernel may send and receive at most23.4 bytes on average; data that exceeds that length can be enqueued ordequeued in a buffer. Each packet 19150 can include header 19152,message digest 19154, data (varies depending on the type of packet)19156, and delimiting mechanism 19158. Delimiting mechanism 19158 canprovide a determination of when one packet ends and the next packetbegins. Consistent overhead byte stuffing (COBS) can provide a fixedoverhead of two bytes for packets of less than 255 data bytes (one extrabyte per packet for encoding, and one extra byte for delimiting),thereby efficiently encoding and decoding each packet. Message digest19154 can provide a means for detecting transmission errors by adding,at the end of packet 19150, extra bytes that are a function of theprevious bytes in the packet, so that a receiver of the packet maycompute the same message digest 19154, and if it matches the onetransmitted, there is high probability that the packet 19150 has arrivedwithout errors. A 16-bit cyclic redundancy check (CRC) can be used insome configurations as a message digest, adding two bytes overhead.

Continuing to still further refer primarily to FIG. 16, beforetransmission, packet 19150 can be formed as a raw data packet, which canhave the 2-byte CRC appended to it, and can be encoded using COBS, forexample. The header can include, but is not limited to including, atleast one byte at the beginning of the raw data packet that candetermine which type of packet it is. Each header 19152 can include, butis not limited to including, a tag that is a prefix code, i.e. withinthe set of possible header tags, in some configurations, no tag is theprefix of any other tag (e.g. the header tags 0xff, 0xfe00, and 0xfe01can be a valid set, but the header tags 0xff, 0xff00 can be an invalidset because 0xff is a prefix of 0xff00). Using this method, 256 validone byte header tags may be developed and more if more than one byte forsome of the header tags is used. In some configurations, the overheadfor packet encoding can be at least one byte for the header tag, twobytes for the CRC, and two bytes for COBS, or five bytes per packet.

Continuing to refer primarily to FIG. 16, there can be a number ofdifferent packet types that can be used for communication protocols. Insome configurations, a ping packet can be sent from DSP 19140 to PC19142 on a periodic basis, or in response to a ping request packet. Theping packet can contain a counter incremented each time a ping packet issent (this allows the PC to detect missing packets), a 16-bit timestamp,and critical message counters (described herein). A ping request packetcan be sent from PC 19142 to DSP 19140 on an arbitrary basis. For“keepalive” purposes, a predetermined timeout of approximately 100 mseccan be used both for ping packets and ping request packets. Both PC19142 and DSP 19140 can transmit the corresponding packet during eachtimeout interval, and if a timeout interval elapses without receivingthe corresponding packet, something could be wrong and thecommunications connection could be considered to be interrupted. Amemory read request can be sent from PC 19142 to DSP 19140 on anarbitrary basis. The memory read request can include an 8-bit readrequest ID, eight bits of flags, an 8-bit byte count, and a 32-bitstarting address. The flags can include one bit determining whether theaddress points to absolute memory or “virtual memory” (describedherein). Upon receiving the memory read request, DSP 19140 can read therequested memory and respond with a memory read response. A memory readresponse can be sent from DSP 19140 to PC 19142 in response to a memoryread request. The memory read response can contain the 8-bit readrequest ID, and data corresponding to the memory read request. Therequest ID can enable the PC 19142 to request several different piecesof data and later match the responses with the requests. If a readresponse is not received, PC 19142 may re-issue the read request. Amemory write request can be sent from PC 19142 to DSP 19140 on anarbitrary basis. The memory write request can contain an 8-bit criticalmessage count, eight bits of flags, a 32-bit starting address, and data.The flags can include one bit indicating whether the address points toabsolute memory or virtual memory. Upon receiving the memory writerequest, DSP 19140 can write the requested memory. A critical messagecount can be maintained by DSP 19140 and reported in a ping packet. Forpacket types that are considered critical messages (including memorywrite requests), DSP 19140 can ignore any message where the receivedcritical message count does not match its internal counter. If thecritical message counts match, DSP 19140 can increment the criticalmessage count and act upon the received message. DSP 19140 and PC 19142can stay in sync with respect to critical messages based on the protocoldescribed herein. If messages are improperly received, they can beignored, and PC 19142 may detect the improper reception and re-sendmessages. If the same message is received twice, the duplicate messagecan elicit a single reaction. A broadcast packet can be sent from DSP19140 to PC 19142. The broadcast packet can include a packet ID headertag, an 8-bit counter field, and data. Header tags 0x00-0x7f forbroadcast packets can be reserved, leaving tags 0x80-0xff for the packettypes described above as well as application-specific packets. Abroadcast packet can be sent once each time a diagnostic kernel of DSP19140 executes, and when DSP 19140 has detected valid communicationsfrom PC 19142 (e.g. it has received a ping request packet within itstimeout). Header tag 19152 can allow twenty-eight different sets of datato be sent.

Continuing to still further refer primarily to FIG. 16, each data setmay have arbitrary data, to the extent that it may fit within theavailable bandwidth. In some configurations, twenty-three bytes can beavailable with four bytes overhead for COBS and the CRC—one byte for thepacket header tag and one byte for the counter field—leaving seventeenbytes for data. In some configurations, fourteen bytes (seven 16-bitwords) can be used. An 8-bit counter field can include a 3-bit changecounter and a 5-bit tick count. The change counter can be incrementedonce each time DSP 19140 executes a memory write request that couldaffect the contents of the broadcast packet, so that, for example, if PC19142 sends a request to DSP 19140 to write memory, the contents of thebroadcast packet could be changed, and PC 19142 may determine exactlywhen DSP 19140 is sending new data. The 5-bit tick count can provide afine-grained timestamp for the data that was sent. The 5-bit tick countcan allow for up to thirty-one broadcast packets to be lost while stillmaintaining a valid timestamp. Ping packet can include the sametimestamp but can use a full sixteen bits. The combination of these twotimestamps can allow PC 19142 to track timestamps even in the presenceof missing packets, and can allow PC 19142 to extrapolate receiveddata—data measured or sensed voltage—without DSP 19140 having toallocate large amounts of bandwidth. PC 19142 can include a copy ofexecutable file 19148 containing a symbol file which can provide for PC19142 to access the memory of DSP 19140.

Referring now primarily to FIG. 17, certain items of data can beaccessed in an area of virtual memory 21164 (FIG. 16) where DSP 19140(FIG. 16) can translate a memory request from PC 19142 (FIG. 16) to amemory address understood by DSP 19140. These items of data can include,but are not limited to including, build metadata providing informationabout executable file 19148 (FIG. 16). If the build metadata inexecutable file 19148 (FIG. 16) does not match the build metadatareceived from DSP 19140 (FIG. 16), then the absolute addresses found inthe symbol table of executable file 19148 (FIG. 16) may not be usedreliably. Data items can also include session ID 21166, an arbitrarynumber created by PC 19142 (FIG. 16) at each communication with DSP19140 (FIG. 16). To protect access to virtual memory 21164 (FIG. 16),method 2100 can include, but is not limited to including, creating 2101,by PC 19142 (FIG. 16), an initial unique session ID, and sending 2103the session ID to DSP 19140 (FIG. 16). DSP 19140 (FIG. 16) can receiveand apply 2105 session ID. If 2123 DSP 19140 (FIG. 16) has been reset,DSP 19140 (FIG. 16) can scramble 2111 session ID 21166. If 2107 PC 19142(FIG. 16) experiences a communications interruption (detected by, forexample, ping packet timeouts), PC 19142 (FIG. 16) can request 2109session ID from DSP 19140 (FIG. 16), and if 2113 session ID 21166 (FIG.16) has changed from a previous reading, then either DSP 19140 (FIG. 16)has been reset, or PC 19142 (FIG. 16) has been connected to a differentDSP 19140 (FIG. 16). PC 19142 (FIG. 16) can then request 2117 executablefiles 19148 (FIG. 16) from DSP 19140 (FIG. 16), DSP 19140 (FIG. 16) cansend 2119 executable files 19148 (FIG. 16), and PC 19142 (FIG. 16) canreceive 2121 executable files 19148 (FIG. 16). If 2113 session ID 21166(FIG. 16) has not changed, PC 19142 (FIG. 16) may assume that atemporary communications interruption has occurred between DSP 19140(FIG. 16) and PC 19142 (FIG. 16) and can continue 2115 using executablefiles 19148 (FIG. 16).

Referring now primarily to FIG. 18, data can also include broadcastmetadata 19146 (FIG. 16) which can include CPU metadata, including flagsthat identify (1) whether the CPU uses 8-bit or 16-bit memory words, (2)whether the CPU uses 16-bit or 32-bit pointers for memory addressing,(3) whether multiple-word quantities are most-significant-word first orleast-significant-word first, and (4) whether memory address alignmentis 1-byte-aligned, 2-byte-aligned, 4-byte-aligned, or 8-byte-aligned.DSP 19140 can use a particular block of virtual addresses to determinewhich data are sent over broadcast packets, including, in someconfigurations, schedule table 22184, data palette 22186, and a fewcounters. Broadcast packet IDs 22182 can correspond to rows of scheduletable 22184. Schedule table 22184 can provide to DSP 19140 theinformation to send for each broadcast packet ID 22182. Each row ofschedule table 22184 can include, but is not limited to including, twopairs of data, A data 22187 and B data 22189, with each pair consistingof index 22188 and count 22190 referring to an entry in broadcast datapalette 22186. Data palette 22186 can include addresses of, for example,16-bit data words that are written by PC 19142 (FIG. 16). Schedule tableindex 22188 and count 22190 can be used as a starting offset and astarting count respectively within data palette 22186. For example, ifrow 0 of A data 22187 contains index 1, count 3, and row 0 of B data22189 contains index 80, count 2, then broadcast packet id 0 can sendthe contents of data palette addresses #1, #2, #3, #80, and #81. Ifschedule table row 1 contains A data 22187 index 30, count 5, and B data22189 index 45, count 1, then the broadcast packet id 1 can send thecontents of data palette addresses #30, #31, #32, #33, #34, and #45. Adata 22187 can, for example, but not limited to, be several words ofdata that can be broadcast at, in some configurations, every 10 kHzcycle, or every other 10 kHz cycle, whereas B data 22189 can, forexample, but not limited to, be one or two words of data of a long listof data, thereby creating a “fast” set of a few data words, and a “slow”set of many data words, making for a flexible system for data transfer.

Continuing to refer primarily to FIG. 18, if PC 19142 (FIG. 16) can setthe contents of data palette 22186 and schedule table 22184, then PC19142 (FIG. 16) can interpret the contents of each broadcast packet andcan associate the contents with the appropriate memory locations in DSP19140 (FIG. 16) that PC 19142 (FIG. 16) selects. In some configurations,DSP 19140 (FIG. 16) can cycle through rows 0 to SCHEDPERIOD-1 ofschedule table index 22188, where SCHEDPERIOD can include a counterlocated, for example, in the virtual address space and may be set by PC19142 (FIG. 16). It is possible for DSP 19140 (FIG. 16) to use anyarbitrary ordering of rows (e.g. 0, 1, 0, 2, 0, 3, 0, 4, 0, 1, 0, 2, 0,3, 0, 4, etc) of schedule table index 22188. If row # of schedule tableindex 22188 can be transmitted as packet ID 22182 of broadcast datapackets, PC 19142 (FIG. 16) may not need to know about this ordering tobe able to interpret the ordering correctly. In some configurations, amechanism can be provided that can set up a desired ordering.

Referring again primarily to FIG. 16, debugging/diagnostic system anduser interface (DiagUI) 19200 can indicate and relay engine operationaldata from engine 11 (FIG. 4G) to technicians, operators and engineers.Operational data for engine 11 (FIG. 4G) may be collected from aplurality of engine sensors and from DSP 19140 and engine control I/OPCB 49 (FIG. 3). The operational data may be optionally stored in amemory storage device, or relayed directly through DiagUI 19200 to theoperator. DiagUI 19200 can enable an operator to read and write data toDSP 19140 of engine 11 (FIG. 4G), and can monitor engine 11 (FIG. 4G)and DSP 19140, and attend to data logging of predetermined operationaldata to evaluate and analyze operational conditions of engine 11 (FIG.4G). DiagUI 19200 can use for example, but not limited to, a highbandwidth data communication channel in real time, and/or DiagUI 19200can buffer data within a given time frame, and/or can take a snapshot ofsensor data at some point in time of the operating data from engine 11(FIG. 4G) and present the data in a coherent form for analysis. DiagUI19200 can read/write data to and from desired variables of enginecontrol I/O PCB 49 (FIG. 3). The read/write function can be an on-demandtask for DiagUI 19200 and can be a one-time task, meaning althoughrepetitive from the operator's perspective, the read/write function toany particular variable can be begun and completed in a short one-timetask. DiagUI 19200 can monitor the proceeding engine operations bydisplaying desired variable values on the screen, for example, throughimmediate evaluation of engine operation, and through recording of datafor later analysis. Reading and writing of variables for example caninclude determining and selecting a desired variable to write to, forexample, a control parameter for engine 11 (FIG. 4G) that the operatordesires to modify such as a voltage gain threshold limit. Monitoring ofa desired variable can include for example, but not limited to,displaying a real time motor current in a table of DiagUI 19200 and thenlogging that value to a data file for subsequent analysis. In someconfigurations, any variable from executable file 19148 can be monitoredand logged. The system can translate, for example, a variable name to anaddress by reading executable file 19148.

Referring now primarily to FIG. 19A, to associate specific unitdefinitions with program variables of DSP 19140 (FIG. 16), typedefdeclarations can be used, for example, but not limited to, to identify avariable by the unit of measure that it represents. Each variable in DSP19140 (FIG. 16) can be associated with a variable type, e.g. unit32_t,an unsigned 32-bit, int16_t, signed 16-bit, and unit8_t, unsigned 8-bit.The typedef declaration can be a synonym used in place of a data type toassociate that variable with specific data, such as a voltage, current,temperature, etc. Typedef int int16_t can create type int16_t 32100 asan equivalent to type int 32103. Typedef int16_t foo and typedef int16_tbar can create types foo 32105 and bar 32107 respectively as equivalentto type int16_t 32101 and type unsigned long 32117. Typedef unsignedlong unit32_t and typedef unsigned long baz can create types unit32_t32115 and baz 32111 respectively as equivalents to type unsigned long32117. Typedefunit32_t blam can create type blam 32113 as equivalent totype unit32_t 32115 and type unsigned long 32117. Typedef bar quux cancreate type quux 32109 as equivalent to type bar 32107, and equivalentto type int16_t 32101, which is equivalent to type int 32103. Anyvariable or set of variables may be defined; for example a set ofcurrent and voltage readings may be defined as current1_S16,voltage1_S16, temp1_S16, current2_U32, voltage2_U32, etc. with each ofthese unit types resolved, in some configurations, to, for example, butnot limited to, a C/C++ native data type. Variable names may be createdwith specific metadata such as an identifier, for example a suffix thatcan include the unit type. The identifiers may be grouped as membersinto a data structure providing for the group of identifiers to becalled under one name, the name being a new valid type name the same asthe fundamental types such as int or long. The structure name may beused in a particular namespace context allowing for variables having thespecial group identifier to be recognized.

Referring now primarily to FIG. 19B, in some configurations, a typedefdeclaration can be made for each identifier and these identifiers can begrouped under a data structure with a special pre-arranged name such as_Unit_Base_Marker_. A typedef declaration can also be made for eachvariable to point to each of the appropriate identifiers. Each variablestring can include the unit base marker suffix and may be recognizedfrom other similarly named variables that are not within the samecontext as those variables of the _Unit_Base_Marker type. For example:

typedef uint16_t U16; typedef int16_t S16; typedef uint32_t U32; typedefint32_t S32; struct _Unit_Base_Marker_ { U16 x000; S16 x001; U32 x002;S32 x003; . . . }These definitions can provide for a variable string having raw valuedata to be automatically associated with a unit definition and therebyconvert the raw data value to an engineering value using a conversionfactor. In some configurations, DiagUI 19200 (FIG. 16) can provide a setof global variables that can each include a unit name, a static address,and unit type. Using the specific address information, DiagUI 19200(FIG. 16) can extract data from DSP 19140 (FIG. 16), can associate thesedata with the specific global variable having that address information,and can create a variable string that can include the unit name,identifier unit type, and the DSP data. For example, a variable stringcan include Voltage1_S16 Vbat. Using typedef and the stored metadatadefining the string, DiagUI 19200 (FIG. 16) can enable DSP data to beassociated with unit definitions. DiagUI 19200 (FIG. 16) can read theDSP output data file with symbol string information to detect a programvariable's type. DiagUI 19200 (FIG. 16) can compare the typedef chain tothe data structure type for the special _Unit_Base_Marker_and, if thetypedef chain is defined within the context of that data structure type,DiagUI 19200 (FIG. 16) may associate a unit definition with thevariable. If the variable type is descended from one of a unit basetype, DiagUI 19200 (FIG. 16) can analyze the name to determine if thename ends in one of the members of the data structure, in this exampleone of the suffixes _S16, _U16, S32, _U32. If the variable name containsone of the suffixes, DiagUI 19200 (FIG. 16) can resolve the variabledata to remove the identifying suffix from the unit name to determinethe global variable. For example, the variable “Voltage1_S16 Vbat” canhave an inferred unit name “Voltage1”. DiagUI 19200 (FIG. 16) can searchthe unit name for the encoded unit definition string, for example“732.0Q15V”. DiagUI 19200 (FIG. 16) can interpret the unit definition as2¹⁵ counts=732.0V and this data can be associated with a programvariable, Vbat, thereby converting the raw value DSP data to anengineering value.

Continuing to refer primarily to FIG. 19B, in some configurations,DiagUI 19200 (FIG. 16) may change the unit definition for any variablein the system any time DiagUI 19200 (FIG. 16) is turned on including,but not limited to, while the system is running. In some configurations,DiagUI 19200 (FIG. 16) may update the unit definitions for variableswhen it is turned on or when it is reinitialized. In someconfigurations, DiagUI 19200 (FIG. 16) may be programmed to update theunit definitions for variables at any time including, but not limitedto, when a user requests DiagUI 19200 (FIG. 16) to update the unitdefinitions for variables, at specific time intervals, and whenever aunit definition for a variable has been updated using DiagUI 19200 (FIG.16). In some configurations, when a unit definition of a variable hasbeen changed using DiagUI 19200 (FIG. 16), DSP 19140 (FIG. 16) canupdate the unit definition of that variable and any unit definitions ofvariables dependent on the unit definition of that variable. Forexample, the unit definition of power may depend on the unit definitionsof voltage and current. Therefore if the unit definitions of voltageand/or current are changed, DSP 19140 (FIG. 16) can update the unitdefinitions of voltage and/or current, and also the unit definition ofpower. In some configurations, various temperatures in the system may bemeasured including, but not limited to, battery temperature, motortemperature, ambient air temperature in various places relative tosystem 100 (FIG. 4G), and the heat sink temperature. In someconfigurations, if a battery is included, the battery temperature mayalter the behavior of a battery charging algorithm. In someconfigurations, the motor and/or heat sink temperature measurements maybe used to measure how much power is flowing in the system. In someconfigurations, the motor and/or heat sink and/or ambient airtemperature measurements may be used as a basis for throttling down theengine or lowering the current limits in the system to reduce heat tosafe levels. In some configurations, the motor and/or heat sink and/orambient air temperature measurements may be used as a basis for runningthe system at less than the optimal power point to allow the system tocool. In some configurations, the motor and/or heat sink and/or ambientair temperature measurements may be used to measure the efficiency ofthe cooling system.

Configurations of the present teachings can be directed to computersystems for accomplishing the methods discussed in the descriptionherein, and to computer readable media containing programs foraccomplishing these methods. The raw data and results can be stored forfuture retrieval and processing, printed, displayed, transferred toanother computer, and/or transferred elsewhere. Communications links canbe wired or wireless, for example, using cellular communication systems,military communications systems, and satellite communications systems.Parts of system 100 (FIG. 4G), for example, can operate on a computerhaving a variable number of CPUs. Other alternative computer platformscan be used.

Some configurations can be directed to software for accomplishing themethods discussed herein, and computer readable media storing softwarefor accomplishing these methods. The various modules described hereincan be executed on the same CPU, or can be executed on different CPUs.In compliance with the statute, some configurations have been describedherein in language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that some configurations arenot limited to the specific features shown and described, since themeans herein disclosed comprise various forms of putting someconfigurations into effect.

Methods 9150 (FIG. 7), 10150 (FIG. 8), 979 (FIG. 10), 150 (FIG. 11), and2100 (FIG. 17) can be, in whole or in part, implemented electronically.Signals representing actions taken by elements of system 100 (FIG. 4G)and other disclosed configurations can travel over at least one livecommunications network 20 (FIG. 4G). Control and data information can beelectronically executed and stored on at least one computer-readablemedium. The system can be implemented to execute on at least onecomputer node in at least one live communications network. Common formsof at least one computer-readable medium can include, for example, butnot be limited to, a floppy disk, a flexible disk, a hard disk, magnetictape, or any other magnetic medium, a compact disk read only memory orany other optical medium, punched cards, paper tape, or any otherphysical medium with patterns of holes, a random access memory, aprogrammable read only memory, and erasable programmable read onlymemory (EPROM), a Flash EPROM, or any other memory chip or cartridge, orany other medium from which a computer can read.

While the present teachings have been described above in terms ofspecific configurations, it is to be understood that they are notlimited to these disclosed configurations. Many modifications and otherconfigurations will come to mind to those skilled in the art to whichthis pertains, and which are intended to be and are covered by both thisdisclosure and the appended claims. It is intended that the scope of thepresent teachings should be determined by proper interpretation andconstruction of the appended claims and their legal equivalents, asunderstood by those of skill in the art relying upon the disclosure inthis specification and the attached drawings.

What is claimed is:
 1. A method for producing DC power for a loadcomprising: starting an engine using power supplied by a relativelysmall power supply supplemented by a capacitor bank; providing outputfrom the Stirling engine to a generator; producing alternating current(AC) power by the generator; converting the AC power to direct current(DC) power; and providing the DC power to the load.
 2. The method as inclaim 1 further comprising: disabling output of the DC power during afirst set of pre-selected conditions.
 3. The method as in claim 1further comprising: limiting a rate of change of current of the DC powerduring a second set of pre-selected conditions.
 4. The method as inclaim 1 further comprising: reducing conducted and radiated emissions ofthe DC power.
 5. The method as in claim 1 further comprising:disconnecting the DC power from the load under a third set ofpre-selected conditions.
 6. The method as in claim 1 further comprising:controlling velocity of the Stirling engine by a motor drive powerboard.
 7. The method as in claim 6 further comprising: inhibitingcurrent flow from the motor drive power board to the capacitor bank. 8.The method as in claim 1 further comprising: powering, by a second powersupply at the starting up of the Stirling engine, system controlelectronics.
 9. The method as in claim 1 further comprising: shuntingexcess of the DC power in the form of heat produced by the Stirlingengine into a shunt load.
 10. The method as in claim 9 furthercomprising: heating water with the heat.
 11. The method as in claim 1further comprising: controlling velocity of the Stirling engine by amotor drive power board and the generator.
 12. The method as in claim 1wherein the first set of pre-selected conditions comprises overcurrentand ground fault conditions.
 13. The method as in claim 1 wherein thesecond set of pre-selected conditions comprises abnormal conditions. 14.The method as in claim 1 wherein the third set of pre-selectedconditions comprises an abnormal overcurrent condition.
 15. The methodas in claim 1 wherein the disconnecting the DC power comprises: shunttripping a DC output breaker during an arc fault condition.
 16. Themethod as in claim 1 further comprising: providing the DC power to anigniter power board, a pump/fan/blower drive, an engine control I/O PCB,a system control PCB, and a power control PCB.
 17. The method as inclaim 1 further comprising: measuring voltage and frequency of a gridsupply; reporting the voltage and frequency via CANbus to a systemcontroller; starting the engine if the grid supply is within apre-selected range of tolerance; and recording the voltage and frequencyin a continuously running log file.
 18. The method as in claim 1 furthercomprising: receiving an angle from a sawtooth waveform generator;representing the angle by a 16-bit value; applying an average incrementto the angle, as the angle sweeps from 0-360°, every 100 secs, theaverage increment having a 32-bit center frequency input and a 16-bitdelta frequency input driven by a PI controller, the center frequencyinput representing a fractional value of the angle, the delta frequencyoscillating about zero; producing a sine/cosine pair for the angle;creating an inverter output waveform based on the sine/cosine pair;computing a phase error signal based on the sine of the angle and thevoltage of the grid supply, the voltage of the grid supply being equalto the cosine of the voltage of the grid supply; multiplying the sine bythe voltage of the grid supply to produce a signal that contains both ACand DC components, the AC component having an amplitude variation basedon the amplitudes of the grid supply and the inverter output waveformand having a frequency equal to 2× the frequency of the grid supply whenthe loop is locked, the DC component having an amplitude variation basedon the phase error between the grid supply and the inverter outputwaveform; low pass filtering the phase error; and eliminating a part ofthe AC component not relevant to control by supplying the filtered phaseerror to the PI controller.
 19. A system for producing DC power for aload comprising: a Stirling engine initially powered by a relativelysmall power supply supplemented by a capacitor bank; a permanent magnetsynchronous motor generator (PMSMG) operably coupled to the Stirlingengine, the PMSMG producing AC current from the output of the poweredStirling engine; a motor drive power board operably coupled to thePMSMG, the motor drive power board converting the AC current to DCpower; and an ARC fault detector operably coupled to an EMI filter and aDC output breaker, the ARC fault detector shunt tripping the DC outputbreaker during a series ARC fault condition, the DC output breakerproviding the DC power to the load when a third set of pre-selectedconditions is false.
 20. The system as in claim 19 further comprising: aDC output board operably coupled to the motor drive power board, the DCoutput board disabling output of the DC power from the motor drive powerboard during a first set of pre-selected conditions.
 21. The system asin claim 19 further comprising: a di/dT limiter operably coupled to theDC output board, the di/dT limiter limiting a rate of change of currentflow of the DC power from the DC output board during a second set ofpre-selected conditions.
 22. The system as in claim 19 wherein the EMIfilter comprises operable coupling to the di/dT limiter, the EMI filterreducing conducted and radiated emissions of the DC power from the di/dTlimiter.
 23. The system as in claim 19 further comprising: a diodeinhibiting current flow from the motor drive power board to thecapacitor bank.
 24. The system as in claim 19 wherein the PMSMG controlsthe velocity of the Stirling engine.
 25. The system as in claim 19wherein the first set of pre-selected conditions comprises overcurrentand ground fault conditions.
 26. The system as in claim 19 wherein thesecond set of pre-selected conditions comprises abnormal conditions. 27.The system as in claim 19 wherein the third set of pre-selectedconditions comprises an abnormal overcurrent condition.
 28. The systemas in claim 19 wherein the PMSMG comprises a 3-phase generator.
 29. Thesystem as in claim 19 wherein the motor drive power board comprises a 12kVA, 3-phase, 4 quadrant AC/DC converter.
 30. The system as in claim 19wherein the EMI filter comprises a 50A filter.
 31. The system as inclaim 19 wherein the DC output breaker comprises a 50A breaker.
 32. Thesystem as in claim 19 wherein the DC power comprises 390 VDC.
 33. Thesystem as in claim 19 wherein the capacitor bank comprises 24.6 mF. 34.The system as in claim 19 further comprising: a system control powersource; and a start-up system control power source.
 35. The system as inclaim 19 wherein the relatively small power supply comprises a 380 VDC@4A power supply.
 36. The system as in claim 19 further comprising amotor controller for a permanent magnetic synchronous motor comprising:an analog/digital converter converting analog sensor signals from thepermanent magnetic synchronous motor to digital signals for use by adigital signal processor, the analog/digital converter comprising halfbridges across a DC bus and an inductor-capacitor-inductor filterproducing three phase AC power at a predetermined voltage and frequency;at least one voltage sensor and at least one current sensor performingthree-phase demodulation of the three phase signals and converting thethree-phase signals to a two-phase orthogonal reference frame; and aposition/velocity estimator receiving speed sensor signals from themotor and compiling a position and velocity estimation of the motor. 37.A method for starting a Stirling engine comprising: powering a first ACpower supply; powering a second AC power supply; starting the Stirlingengine by the first AC power supply and a capacitor bank; and startingsystem control electronics by the second AC power supply, the systemcontrol electronics controlling a power control board, the power controlboard controlling the Stirling engine.